UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM20-F

(Mark One)

OR

For the fiscal year ended December 31, 2015.2017.

OR

OR

Date of event requiring this shell company report

For the transition period from                 to                

Commission file number:001-35126

21Vianet Group, Inc.

(Exact Name of Registrant as Specified in Its Charter)

N/A

(Translation of Registrant’s Name into English)

Cayman Islands

(Jurisdiction of Incorporation or Organization)

M5, 1 Jiuxianqiao East Road,

Chaoyang District

Beijing, 100016

The People’s Republic of China

(Address of Principal Executive Offices)

Mr. Terry Wang,Ms. Sharon Xiao Liu, Chief Financial Officer

21Vianet Group, Inc.

M5, 1 Jiuxianqiao East Road,

Chaoyang District

Beijing, 100016

The People’s Republic of China

Phone: (86) 10 8456-2121

Facsimile: (86) 10 8456-26198456-4234

(Name, Telephone,E-mail and/or Facsimile Number and Address of Company Contact Person)

Securities registered or to be registered pursuant to Section 12(b) of the Act:

Securities registered or to be registered pursuant to Section 12(g) of the Act:

None

(Title of Class)

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act:

None

(Title of Class)

Indicate the number of outstanding shares of each of the Issuer’s classes of capital or common stock as of the close of the period covered by the annual report: 458,916,346496,636,128 Class A ordinary shares issued and 63,596,248outstanding and excluding treasury shares, and 174,649,638 Class B ordinary shares, par value US$0.00001 per share, as of December 31, 2015.2017.

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  x☐    No  ¨☒

If this report is an annual or transition report, indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.    Yes  ¨☐    No  x☒

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x☒    No  ¨☐

Indicate by check mark whether the registrant has submitted electronically and posted on its Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of RegulationS-T (§232.405 of this chapter) during the preceding 12 months (or such shorter period that the registrant was required to submit and post such files).    Yes  x☒    No  ¨☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, anon-accelerated filer, or a non-accelerated filer.an emerging growth company. See definition of “large accelerated filer,” “accelerated filer ”, and large accelerated filer”“emerging growth company” in Rule12b-2 of the Exchange Act. (Check one):

Large accelerated filer  x                Accelerated filer  ¨                Non-accelerated filer  ¨

If an emerging growth company that prepares its financial statements in accordance with U.S. GAAP, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards† provided pursuant to Section 13(a) of the Exchange Act.  ☐

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing:

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow.

Item 17  ¨☐                Item 18  ¨☐

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule12b-2 of the Exchange Act).    Yes  ¨☐    No  x☒

(APPLICABLE ONLY TO ISSUERS INVOLVED IN BANKRUPTCY PROCEEDINGS DURING THE PAST FIVE YEARS)

Indicate by check mark whether the registrant has filed all documents and reports required to be filed by Sections 12, 13 or 15(d) of the Securities Exchange Act of 1934 subsequent to the distribution of securities under a plan confirmed by a court.    Yes ¨☐    No ¨☐

TABLE OF CONTENTS

i

INTRODUCTION

Unless otherwise indicated and except where the context otherwise requires, references in this annual report on Form20-F to:

FORWARD-LOOKING STATEMENTS

This annual report on Form20-F contains forward-looking statements that involve risks and uncertainties. All statements other than statements of historical facts are forward-looking statements. These forward-looking statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. Known and unknown risks, uncertainties and other factors, including those listed under “Risk Factors,” may cause our actual results, performance or achievements to be materially different from those expressed or implied by the forward-looking statements.

You can identify some of these forward-looking statements by words or phrases such as “may,” “will,” “expect,” “anticipate,” “aim,” “estimate,” “intend,” “plan,” “believe,” “is/are likely to,” “potential,” “continue” or other similar expressions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. These forward-looking statements include:

These forward-looking statements involve various risks and uncertainties. Although we believe that our expectations expressed in these forward-looking statements are reasonable, our expectations may later be found to be incorrect. Our actual results could be materially different from our expectations. Other sections of this annual report include additional factors that could adversely impact our business and financial performance. Moreover, we operate in an evolving environment. New risk factors and uncertainties emerge from time to time and it is not possible for our management to predict all risk factors and uncertainties, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. You should read thoroughly this annual report and the documents that we refer to with the understanding that our actual future results may be materially different from and worse than what we expect. We qualify all of our forward-looking statements by these cautionary statements.

PART I

Not applicable.

Not applicable.

Selected Consolidated Financial Data

The following selected consolidated financial information for the periods and as of the dates indicated should be read in conjunction with our consolidated financial statements and related notes and “Item 5. Operating and Financial Review and Prospects” in this annual report.

Our selected consolidated financial data presented below for the years ended December 31, 2013, 20142015, 2016 and 20152017 and our balance sheet data as of December 31, 20142016 and 20152017 have been derived from our audited consolidated financial statements included elsewhere in this annual report. Our audited consolidated financial statements are prepared in accordance with U.S. GAAP.

Our selected consolidated financial data presented below for the year ended December 31, 20112013 and 20122014 and our balance sheet data as of December 31, 2011, 20122013, 2014 and 20132015 have been derived from our audited financial statements not included in this annual report.

Starting in 2016, we began reporting our operating results in two operating segments, namely hosting and related services and managed network services. Content delivery network services, or CDN services, which were previously offered as part of our hosting and related services business segment, were moved to the managed network services business segment in the fourth quarter of 2016. Our consolidated statements of operations for the years ended December 31, 2014, 2015 and 2016 as presented in this annual report were modified to reflect this change in segment reporting for consistency purposes. Our consolidated states of operation for the years ended December 31, 2013 were not modified to reflect such change.

		For the Year Ended December 31,
		2011				2012				2013				2014				2015
		RMB				RMB				RMB				RMB				RMB				US$
		(in thousands, except share and per share data)
Earnings (loss) per share:
Basic			0.07				0.16				(0.13	)			(0.89	)			(0.85	)			(0.13	)
Diluted			0.06				0.16				(0.13	)			(0.89	)			(0.85	)			(0.13	)
Earnings (loss) per ADS:
Basic			0.42				0.96				(0.78	)			(5.34	)			(5.10	)			(0.79	)
Diluted			0.36				0.96				(0.78	)			(5.34	)			(5.10	)			(0.79	)
Shares used in earnings (loss) per share computation:
Basic			259,595,677				342,533,167				364,353,974				401,335,788				492,065,239				492,065,239
Diluted			316,807,661				356,784,209				364,353,974				401,335,788				492,065,239				492,065,239
Non-GAAP Financial Data:(2)
Adjusted gross profit			307,103				457,381				568,670				924,228				1,023,299				157,970
Adjusted net profit (loss)			169,993				167,287				120,466				79,374				(10,804	)			(1,668	)
Adjusted EBITDA			209,026				294,165				365,613				558,938				540,411				83,425

In September 2017, we completed the disposal of our managed network services business segment, including CDN services, hosting area network services, route optimization and last-mile broadband businesses, and deconsolidated the financial results related to the managed network services business segment in our consolidated statements of operations starting from the fourth quarter of 2017.

The following table presents a summary of our consolidated balance sheet data as of December 31, 2011, 2012, 2013, 2014 and 2015.

Discussion of Non-GAAP Financial Measures

In evaluating our business, we consider and use the following non-GAAP measures as supplemental measures to review and assess our operating performance: adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA. The presentation of these non-GAAP financial measures is not intended to be considered in isolation or as a substitute for the financial information prepared and presented in accordance with U.S. GAAP. We define adjusted gross profit as gross profit excluding share-based compensation expenses and amortization expenses of intangible assets derived from acquisitions. We define adjusted operating expenses as operating income (expenses) excluding share-based compensation expenses, changes in the fair value of contingent purchase consideration payable and operating income. We define adjusted net profit as net (loss) profit from continuing operations excluding share-based compensation expenses, amortization expenses of intangible assets derived from acquisitions, changes in the fair value of contingent purchase consideration payable and loss on debt extinguishment. We define adjusted EBITDA as EBITDA excluding share-based compensation expenses, changes in the fair value of contingent purchase consideration payable and loss on debt extinguishment, and EBITDA as net profit (loss) from continuing operations before income tax expense (benefit), foreign exchange gain (loss), other expenses, other income, interest expense, interest income and depreciation and amortization.

The non-GAAP financial measure disclosed by us should not be considered a substitute for financial measures prepared in accordance with U.S. GAAP. You should carefully evaluate the financial results we have reported in accordance with U.S. GAAP and our reconciliation of GAAP to non-GAAP results. The non-GAAP financial measure used by us may be prepared differently from and, therefore, may not be comparable to similarly titled measures used by other companies.

We believe that the use of these non-GAAP measures facilitates investors’ assessment of our operating performance from period to period and from company to company by backing out potential differences caused by variations in items such as capital structures (affecting relative interest expenses), the book amortization of intangibles (affecting relative amortization expenses), the age and book value of property and equipment (affecting relative depreciation expenses) and other non-cash expenses (affecting share-based compensation expenses). We also present these non-GAAP measures because we believe these non-GAAP measures are frequently used by securities analysts, investors and other interested parties as measures of the financial performance of companies in our industry.

These non-GAAP financial measures are not defined under U.S. GAAP and are not measures presented in accordance with U.S. GAAP. These non-GAAP financial measures have limitations as analytical tools, and when assessing our operating performance, investors should not consider them in isolation, or as a substitute for net income (loss) or other consolidated income statement data prepared in accordance with U.S. GAAP. Some of these limitations include, but are not limited to:

We compensate for these limitations by relying primarily on our U.S. GAAP results and using adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA only as supplemental measures. Our adjusted gross profit, adjusted operating expenses, adjusted net profit and adjusted EBITDA are calculated as follows for the periods presented:

Exchange Rate Information

Most of our operations are conducted in China and most of our revenues are denominated in Renminbi. This annual report contains translations of Renminbi amounts into U.S. dollars at specific rates solely for the

convenience of the reader. The conversion of RMB into U.S. dollars in this annual report is based on the noon buying rate in New York City for cable transfers of RMB as certified for customs purposes by the Federal Reserve Bank of New York. Unless otherwise noted, all translations from RMB to U.S. dollars and from U.S. dollars to RMB in this annual report were made at a rate of RMB6.4778RMB6.5063 to US$1.00, the noon buying rate in effect as of December 31, 2015.29, 2017. We make no representation that any RMB or U.S. dollar amounts could have been, or could be, converted into U.S. dollars or RMB, as the case may be, at any particular rate, or at all. The PRC government imposes control over its foreign currency reserves in part through direct regulation of the conversion of RMB into foreign exchange and through restrictions on foreign trade. On April 8, 2016,6, 2018, the noon buying rate was RMB6.4628RMB6.3045 to US$1.00.

The following table sets forth information concerning exchange rates between the RMB and the U.S. dollar for the periods indicated.

Source: Federal Reserve Statistical Release

Note:

Not applicable.

Not applicable.

Risks Related to Our Business and Industry

We may not be able to successfully implement our growth strategies.

We plan to further increase our services capacities. In 2015,2017, we increased the aggregate number of cabinets under our management by 2,0002,700 to more than 23,500.29,080. In order to support our growing customer demand, we plan to add new cabinets in 20162018 through new self-built data centers, new phases of existing self-built data centers and partnered data centers.centers, which will include those through our partnership with Warburg Pincus. In addition, we plan to expand our private optical fiber network to cover all of our major

data centers throughout China and plan to increase our network services capacity. To achieve this expansion plan, we will be required to commit a substantial amount of operating and financial resources. Our planned capital expenditures, together with our ongoing operating expenses, will cause substantial cash outflows. If we are not able to generate sufficient operating cash flows or obtain alternative financings, our ability to fund our growth strategy may be limited. Alternative debt or equity financing may not be available when needed or, if available, may not be available on satisfactory terms. Any inability to obtain additional debt or equity financing or to generate sufficient cash from operations may require us to prioritize projects or curtail capital expenditures and could adversely affect our results of operations.

In addition, site selection is a critical factor in our expansion plans, and there may not be suitable properties available with the necessary combination of high power capacity and optical fiber connectivity, which may have a negative impact on our revenue growth. Moreover, we may not have sufficient customer demand in the markets where our data centers are located. We may overestimate the demand for our services and as a result may increase our data center capacity or expand our internet network more aggressively than needed, resulting in a negative impact to our gross profit margins. Furthermore, the costs of construction and maintenance of new data centers constitute a significant portion of our capital expenditures and operating expenses. If our planned expansion does not achieve the desired results, our operating margins could be materially reduced, which would materially impair our profitability and adversely affect our business and results of operations.

Delays in the construction of new data centers or the expansion of existing data centers could involve significant risks to our business.

In order to meet customer demand in some of our existing and new markets, we need to expand existing data centers, lease new facilities or obtain suitable land to build new data centers. Expansion of existing data centers and/or construction of new data centers are currently underway, or being contemplated, in many of our markets. Such expansion and/or construction require us to carefully select and rely on the experience of one or more designers, general contractors, and subcontractors during the design and construction process. If a designer, general contractor, or significant subcontractor experiences financial or other problems during the design or construction process, we could experience significant delays and/or incur increased costs to complete the projects, resulting in negative impacts on our results of operations.

In addition, we need to work closely with the local power suppliers where our proposed data centers are located. If we experience significant delays in the supply of power required to support the data center expansion or new construction, either during the design or construction phases, the progress of the data center expansion and/or construction could deviate from our original plans, which could cause material and negative effect to our revenue growth, profitability and results of operations.

Any significant or prolonged failure in our infrastructure or services would lead to significant costs and disruptions and would reduce our revenues, harm our business reputation and have a material adverse effect on our financial results.

Our data centers, power supplies and network are vulnerable to disruptions and to failure. Problems with the cooling equipment, generators, backup batteries, routers, switches, or other equipment, whether or not within our control, could result in service interruptions and data losses for our customers as well as equipment damage. Our customers locate their computing and networking equipment in our data centers, and any significant or prolonged failure in our infrastructure or services could significantly disrupt the normal business operations of our customers and harm our reputation and reduce our revenue. While we offer data backup services and disaster recovery services, which could mitigate the adverse effects of such a failure, most of our customers do not subscribe for these services. Accordingly, any failure or downtime in one of our data centers could affect many of our customers. The total destruction or severe impairment of any of our data centers could result in significant downtime of our services and loss of customer data. Since our ability to attract and retain customers depends on our ability to provide highly reliable service, even minor interruptions in our service could harm our reputation.

While we have not experienced any material interruptions in the past, services interruptions continue to be a significant risk for us and could materially impact our business. Any services interruptions could:

Any of these events could materially increase our expenses or reduce our revenue, which would have a material adverse effect on our results of operations.

We depend on third-party suppliers for key elements of our network infrastructure, data center and telecommunication network services, and we also compete with and our business substantially depends on,some of the third-party suppliers, primarily China Telecom and China Unicom, for hosting facilities and othercertain telecommunication resources.

Our businesssuccess depends onin part upon our relationships with third-party suppliers, primarily China Telecom andor China Unicom, two major telecommunications carriers in China, for key elements of network infrastructure and telecommunication network services, including hosting facilities and bandwidth, and to some extent, for optical fibers. We directly enter into agreements with the local subsidiaries of China Telecom or China Unicom, from which we lease cabinets in the data centers built and operated by them, with power systems, cabling and wiring and other data center equipmentpre-installed. Because each local subsidiary of China Telecom or China Unicom has independent authority and budget to enter into contracts, our contract terms with these subsidiaries vary and are determined on acase-by-case basis. We generally define “partnered” data centers as the data center space and cabinets we leased from China Telecom, China Unicom and other third parties through agreements. Based on the specific requests of our customers, demands in different cities and our strategy for points of presence, or POP, establishment, the locations and number of our partnered data centers may change from time to time. As of December 31, 2015,2017, we leased a total of 7,5585,257 cabinets that are housed in our 6938 partnered data centers, accounting for 32.1%18.1% of the total number of our cabinets under management. If we are not able to secure sufficient cabinets from China Unicom and China Telecom, it will have a material adverse effect on our business prospects and results of operations.

We also rely on our internet bandwidth suppliers, which are primarily China Telecom and China Unicom, for a significant portion of our bandwidth needs and lease optical fibers from them to connect our data centers with each other and with the telecommunications backbones and other internet service providers, or ISPs. Our agreements with local subsidiaries of China Telecom or China Unicom usually have aone-year term with automatic renewal option. In addition, We can offer no assurances that these service providers will continue to provide service to us on a cost-effective basis or on otherwise competitive terms, if at all, or that these providers will provide us with additional capacity to adequately meet customer demand or to expand our business. Any of these factors could limit our growth prospects and materially and adversely affect our business.

China Telecom and China Unicom also provide data center and bandwidth services and directly compete with us for customers.while we exercise little control over them. See “—We may not be able to compete effectively against our current and future competitors.” We believe that we have good business relationships with China Telecom and China Unicom, and we have access to adequate hosting facilities bandwidth and optical fibersbandwidth to provide our services. However, there can be no assurance that we can always secure hosting facilities and bandwidth from China Telecom and China Unicom on commercially acceptable terms, or at all. As

We also depend on third-party suppliers for optical fibers for our data transmission network. We offer no assurance that we will be able to maintain a result,good relationship with our optical fiber providers or renew our leases on commercially reasonably terms, if at all. The occurrence of these events would materially and adversely affect our ability to provide services and affect our business and results of operations wouldoperations.

In addition, we currently purchase routers, switches and other equipment from a limited number of suppliers. We do not carry significant inventories of the products we purchase, and we have no guaranteed supply arrangements with our suppliers. The loss of a significant vendor could delay anybuild-out of our infrastructure and increase our costs. If our suppliers fail to provide products or services that comply with evolving internet standards or that interoperate with other products or services we use in our network infrastructure, we may be unable to meet all or a portion of our customer service commitments, which could materially and adversely affected.affect our results of operations.

Furthermore, we have experienced and expect to continue to experience interruptions or delays in network services. Any failure on our part or the part of our third-party suppliers to achieve or maintain high data transmission capacity, reliability or performance could significantly reduce customer demand for our services and damage our business and reputation. As our customer base grows and their usage of telecommunications resources increases, we may be required to make additional investments in our capacity to maintain adequate data transmission speed. The availability of such capacity may be limited or the cost may be unacceptable to us. If adequate capacity is not available to us as our customers’ usage increases, our network may be unable to achieve or maintain sufficiently high data transmission capacity, reliability or performance. In addition, our operating margins may suffer if our bandwidth suppliers increase the prices for their services and we are unable to pass along the increased costs to our customers.

Our leases for data centers could be terminated early, we may not be able to renew our existing leases on commercially reasonable terms, and our rent could increase substantially in the future, which could materially and adversely affect our operations.

We lease buildings with suitable power supplies and safe structures meeting our data center requirements and convert them into data centers by installing power generators, air conditioning systems, cables, cabinets and other equipment. We also build our own data centers from the ground up after obtaining suitable land. For a small portion of our data centers, we purchase data center equipment and install them in a property with already installed infrastructure and then lease the data center back to such property owner. We generally refer to these

three types of data centers as “self-built” data centers. Our operating leases generally have three to twenty years lease terms with renewal options. As of December 31, 2015,2017, our self-built data centers house 15,99823,823 cabinets, or 67.9%81.9% of the total number of our cabinets under our management. We plan to renew our existing leases upon expiration. However, we may not be able to renew these leases on commercially reasonable terms, if at all. We may experience an increase in our rent payments. In addition, although the lessors of our self-built data centers generally do not have the right of early termination and we have not experienced any early termination as of the date of this annual report, the lease could be terminated early if we are in material breach of the lease agreements or the leased premises become unavailable due to reasons beyond the lessors’ control. If our leases for data centers were terminated early, we may have to relocate our data center equipment and the servers and equipment of our customers to a new building and incur significant costcosts related to relocation. Any relocation could also affect our ability to provide services and harm our reputation. As a result, our business and results of operations could be materially and adversely affected.

We have been named as a defendant in a putative shareholder class action lawsuit that could have a material adverse impact on our business, financial condition, results of operation, cash flows and reputation.

We will have to defend against the putative shareholder class action lawsuit described in “Item 8. Financial Information—A. Consolidated Statements and Other Financial Information—Legal and Administrative Proceedings—Litigation,” including any appeals of such lawsuits should our initial defense be unsuccessful. We areOn April 9, 2018, the lead plaintiff of the putative class action filed an unopposed motion for preliminary approval of class action settlement, requesting that, among others, the Court preliminarily approve a settlement agreement that the parties reached to settle the case for US$9,000,000. The unopposed motion for preliminary approval is currently unable topending before the Court. In the event that the proposed settlement is not approved by the Court and/or is not consummated for any other reason, we will not be able estimate the possible loss or possible range of loss, if any, associated with the resolution of these lawsuits.this lawsuit. In the event that our initial defense of these lawsuits is unsuccessful, there can be no assurance that we will prevail in any appeal. Any adverse outcome of these cases, including any plaintiff’s appeal of a judgment in these lawsuits, could have a material adverse effect on our business, financial condition, results of operation, cash flows and reputation. In addition, there can be no assurance that our insurance carriers will cover all or part of the defense costs, or any liabilities that may arise from these matters. The litigation process may utilize a significant portion of our cash resources and divert management’s attention from theday-to-day operations of our company, all of which could harm our business. We also may be subject to claims for indemnification related to these matters, and we cannot predict the impact that indemnification claims may have on our business or financial results.

Investment in broadband wireless access services in Hong Kong may have a material adverse effect on our business prospects and results of operations.

In February 2012, we won a bid for radio spectrum in the 2.3 GHz band to provide broadband wireless access services in Hong Kong for HK$150 million. In August 2015, the Hong Kong Communications Authority agreed to our proposal to provide fixed wireless broadband service to rural villages in Hong Kong to fulfill a revised set of network and service rollout requirements for the release of a performance bond in the amount of HK$150 million submitted by us to the Hong Kong Communications Authority. Currently, we plan to incur a small amount of capital expenditure to build the infrastructures in rural areas in Hong Kong by ourselves. However, we may not be able to successfully rollout our network in rural villages in time to meet the requirements of the Hong Kong Communications Authority and the performance bond may be withheld if we fail to successfully fulfill the revised requirements for the broadband wireless access license by ourselves, and furthermore, our investment in the broadband wireless access license may divert our management’s attention from our core business in mainland China, which would have a material adverse effect on our business prospects and results of operations.

Difficulties in identifying, consummating and integrating acquisitions and alliances and potentialwrite-off in connection with our investment or acquisitions may have a material and adverse effect on our business and results of operations.

As part of our growth strategy, we have acquired, and may in the future acquire, companies that are complementary to our business. From time to time, we may also make alternative investments and enter into strategic partnerships or alliances as we see fit. For example, in October 2012, we entered into a commercial

operator agreement with Microsoft Corporation to expand Microsoft’s premier commercial public cloud services, Office 365 and Windows Azure, in China, and we further agreed with them to extend the term of which was extended to December 31,agreement and establish a long-term partnership in March 14, 2018. In February 2013, we acquired 100% equity interests in Beijing Tianwang Online Communication Technology Co., Ltd. (which later changed its name to WiFire (Beijing) Technology Co., Ltd.), or WiFire BJ, and Beijing Yilong Xinda Technology Co., Ltd., or BJ Yilong. These two companies principally provide virtual private network services and managed network services. In April 2013, we completed the acquisition of 100% equity interests in iJoy Holding Limited, or iJoy BVI, and its subsidiaries (collectively known as “iJoy”) with a purchase consideration of RMB97.0 million. In June 2013, we entered into a strategic agreement with Dongguan Dongcai Investment Holdings Limited, or Dongguan Dongcai, and established Dongguan Asia Cloud Investment Co., Ltd., or Asia Cloud Investment, with the intention to build a new internet data center, provide cloud computing related services in Dongguan as well as create a research and development team that will focus on developing and implementing next generation networking technologies. In December 2013, we entered into a definitive agreement with IBM to introduce IBM’s premier private cloud infrastructure service and bring high-value managed private and hybrid cloud services to China and in October 2016, we launched IBM Bluemix cloud services which are now generally available in China. IBM willIn September 2015, we signed a memorandum of understanding with Unisplendour Corporation Limited (UNIS) and Microsoft to provide the physical point of distribution, or POD,customized hybrid cloud computing solutions and service whilerelated services to Chinese users. In March 2017, we will host the POD facility at our data centersentered into an investment agreement with Warburg Pincus to establish a multi-stage joint venture and build a digital real estate platform in Beijing. In May 2014,China, pursuant to which we acquired 50% equity interests plus one share in Sichuan Aipu Network Co., Ltd. and its affiliates (collectively, the “Aipu Group”). Aipu Group principally provides last-mile wired broadband accessWarburg Pincus agreed to contribute assets, capital and other value-added services.resources to this joint venture. In August 2014,November 2017, we acquired 100% equity interestsentered in Dermot Holdings Limitedto a definitive agreement with BMW to provide a cutting-edge turnkey solutions to BMW, as well as private and its subsidiaries (collectively, the “Dermot Entities”)hybrid cloud services, to expand our data transmission infrastructure across the Greater China region and deliver high-performance virtual private network (VPN) connectivity solutions by utilizing Dermot Entities’ advanced network and infrastructure.support BMW’s strong capacity needs in China. However, past and future acquisitions, partnerships or alliances may expose us to potential risks, including risks associated with:

Any of the potential risks listed above could have a material and adverse effect on our ability to manage our business and our results of operation. For example, Asia Cloud Investment and its subsidiary, Dongguan Asia Cloud Network Technology Co., Ltd., have not commenced any significant operations except for investments in certain floating rate principal unguaranteed securities with an aggregate amount of RMB102.3 million. The intended business purpose of Asia Cloud Investment may prove to be unsuccessful, which could have an adverse effect on our results of operation.

In addition, we record goodwill if the purchase price we pay in the acquisitions exceeded the amount assigned to the fair value of the net assets or business acquired. We are required to test our goodwill and intangible assets for impairment annually or more frequently if events or changes in circumstances indicate that

they may be impaired. We may record impairment of goodwill and acquired intangible assets in connection with our acquisitions if the carrying value of our acquisition goodwill and related acquired intangible assets in

connection with our past or future acquisitions are determined to be impaired. We cannot be assured the acquired businesses, technologies, services and products from our past acquisitions and any potential transaction will generate sufficient revenue to offset the associated costs or other potential unforeseen adverse effects on our business. Furthermore, we may need to raise additional debt or sell additional equity or equity-linked securities to make or complete such acquisitions. See “—We may require additional capital to meet our future capital needs, which may adversely affect our financial position and result in additional shareholder dilution.”

We may not be able to increase sales to our existing customers and add new customers, which would adversely affect our results of operations.

Our growth depends on our ability to continue to expand our service offerings to existing customers and attract new customers. We may be unable to sustain our growth for a number of reasons, such as:

A substantial amount of our past revenues were derived from service upgrades by existing customers. Our costs associated with increasing revenues from existing customers are generally lower than costs associated with generating revenues from new customers. Therefore, slowing revenue growth or declining revenues from our existing customers, even if offset by an increase in revenues from new customers, could reduce our operating margins. Any failure to continue attracting new customers or grow our revenues from existing customers for a prolonged period of time could have a material adverse effect on our results of operations.

We may not be able to compete effectively against our current and future competitors.

We face competition from various industry players, including carriers such as China Telecom and China Unicom, carrier-neutral service providers in China such as SINNET, GDS and Dr. Peng, content delivery network (CDN) service provider such as ChinaCache and ChinaNetCenter, cloud services providers such as AliCloud and Tencent Cloud, as well as new market entrants in the future. As we enter into the last-mile wired broadband market and VPN market, we face competition from Great Wall Broadband Network and Citic Telecom CPC, respectively.China Telecom, PCCW, and CBCcom. Competition is primarily centered on the quality of service and technical expertise, security, reliability and functionality, reputation and brand recognition, financial strength, the breadth and depth of services offered, and price. Some of our current and future competitors have substantially greater financial, technical and marketing resources, greater brand recognition, and more established relationships in the industry than we do. As a result, some of these competitors may be able to:

If we are unable to compete effectively and successfully against our current and future competitors, our business prospects, financial condition and results of operations could be materially and adversely affected.

We depend on third-party suppliers for key elements of our network infrastructure, and our financial performance and results of operation could suffer if we fail to manage supplier issue properly.

To provide connectivity services to our customers, we purchase network connections from several network service providers, primarily China Telecom and China Unicom. We can offer no assurances that these service providers will continue to provide service to us on a cost-effective basis or on otherwise competitive terms, if at all, or that these providers will provide us with additional capacity to adequately meet customer demand or to expand our business. Any of these factors could limit our growth prospects and materially and adversely affect our business.

We also depend on third parties for optical fibers for our data transmission network. We offer no assurance that we will be able to maintain a good relationship with our optical fiber providers or renew our leases on commercially reasonably terms, if at all. The occurrence of these events would materially and adversely affect our ability to provide services and affect our business and results of operations.

In addition, we currently purchase routers, switches and other equipment from a limited number of suppliers. We do not carry significant inventories of the products we purchase, and we have no guaranteed supply arrangements with our suppliers. The loss of a significant vendor could delay any build-out of our infrastructure and increase our costs. If our suppliers fail to provide products or services that comply with evolving internet standards or that interoperate with other products or services we use in our network infrastructure, we may be unable to meet all or a portion of our customer service commitments, which could materially and adversely affect our results of operations.

Our self-built and partnered data centers are vulnerable to security breaches, which could disrupt our operations and have a material adverse effect on our business, financial performance and results of operations.

A party who is able to compromise the security measures of our data centers and networks or the security of our infrastructure could misappropriate either our proprietary information or the information of our customers, or cause interruptions or malfunctions in our operations. In addition, we have limited control over our partnered data centers, which are primarily operated by China Telecom or China Unicom. We may be required to devote significant capital and resources to protect against such threats or to alleviate problems caused by security breaches. As techniques used to breach security change frequently and are generally not recognized until launched against a target, we may not be able to implement security measures in a timely manner or, if and when implemented, we may not be certain whether these measures could be circumvented. Any breaches that may occur could expose us to increased risk of lawsuits, regulatory penalties, loss of existing or potential customers, harm to our reputation and significant increases in our security costs, which could have a material adverse effect on our financial performance and results of operations.

We depend on third parties for telecommunication network services, and increased telecommunications costs may adversely affect our results of operations.

Our success depends in part upon the capacity, reliability, and performance of our network infrastructure, including the capacity leased from our internet bandwidth suppliers, which are primarily China Telecom and

China Unicom. We depend on these companies to provide us with uninterrupted and error-free services through their telecommunications networks. However, some of these providers are also our competitors and we exercise little control over our bandwidth suppliers. In addition, we have experienced and expect to continue to experience interruptions or delays in network services. Any failure on our part or the part of our third-party suppliers to achieve or maintain high data transmission capacity, reliability or performance could significantly reduce customer demand for our services and damage our business and reputation.

As our customer base grows and their usage of telecommunications resources increases, we may be required to make additional investments in our capacity to maintain adequate data transmission speed. The availability of such capacity may be limited or the cost may be unacceptable to us. If adequate capacity is not available to us as our customers’ usage increases, our network may be unable to achieve or maintain sufficiently high data transmission capacity, reliability or performance. In addition, our operating margins may suffer if our bandwidth suppliers increase the prices for their services and we are unable to pass along the increased costs to our customers.

A severe or prolonged downturn in the global or Chinese economy could materially and adversely affect our business and our results of operation.

The global macroeconomic environment is facing challenges, including the escalation of the European sovereign debt crisis since 2011, the end of quantitative easing by the U.S. Federal Reserve and the economic slowdown in the Eurozone in 2014. Our business and operations are primarily based in China and most of our revenues are derived from our operations in China. Accordingly, our financial results have been, and are expected to continue to be, affected by the economy and data center services industry in China. Although the economy in China has grown significantly in the past decades, it still faces challenges. The Chinese economy has slowed down in recent years. According to the National Bureau of Statistics of China, China’s gross domestic product (GDP) growth slowed to 6.9% in 2015.2017. There is considerable uncertainty over the long-term effects of the expansionary monetary and fiscal policies adopted by the central banks and financial authorities of some of the world’s leading economies, including the United States and China. There is considerable uncertainty surrounding the policy decisions the Trump Administration in the United States will make, especially in regard to foreign policy, which may impact the relationship between China and the United States. There have been concerns over unrest and terrorist threats in the Middle East and Africa, which have resulted in volatility in oil and other markets, and over the conflicts involving Ukraine and Syria. There have also been concerns on the relationship among China and other countries, including surrounding Asian countries, which may resultpotentially lead to foreign investors closing down their business or withdrawing their investment in or intensify potential conflicts in relation to territorial disputes.China and thus existing the China market, and other economic effects. Economic conditions in China are sensitive to global economic conditions, as well as changes in domestic economic and political policies and the expected or perceived overall economic growth rate in China. Any prolonged slowdown in the global or Chinese economy may have a negative impact on our business, results of operations and financial condition, and continued turbulence in the international markets may adversely affect our ability to access the capital markets to meet liquidity needs.

If we are unable to meet our customers’ requirements, our reputation and results of operations could suffer.

Our agreements with our customers contain certain guarantees regarding our performance. For hosting services, we guarantee 99.99% uptime for power and 99.9% uptime for network connectivity, failure of which

will cause us to provide free service for a following period of time. In 2016, one of our data centers in southern China experienced a network outage for an extended period of time due to supplier-side connectivity issues. As a result, we failed to meet the 99.9% uptime for network connectivity and provided free service for a following month. Although weperiod of time to all customers who were affected pursuant to customer contracts. This is aone-time incident and did not have not had any material customer claims for power failures or network disruptions, our success dependsimpact on our ability to meet or exceed our customers’ expectations. We have not had any major customer service issuesbusiness. If in the past. However, if in the future similar incidents were to recur or we are unable to provide customers with quality customer support, we could face customer dissatisfaction, decreased overall demand for our services, and loss of revenue. In addition, inability to meet customer service expectations may damage our reputation and could consequently limit our ability to retain existing customers and attract new customers, which would adversely affect our ability to generate revenue and negatively impact our results of operations.

We rely on customers in the internet industry for most of our revenues.

We derived a majority of our revenues in 20152017 from customers in China’s internet industry, including online media,e-commerce, live broadcasting, social networks, online game companies, portals, search engines, mobile internet and cloud services

providers. The business models of some internet companies are relatively new and have not been well proven. Many internet companies base their business prospects on the continued growth of China’s internet market, which may not happen as expected.

In addition, our business would suffer if companies in China’s internet sector reduce the outsourcing of their data center services. If any of these events happen, we may lose customers or have difficulties in selling our services, which would materially and adversely affect our business and results of operations.

We may require additional capital to meet our future capital needs, which may adversely affect our financial position and result in additional shareholder dilution.

We will require significant capital expenditures to fund our future growth. We may need to raise additional funds through equity or debt financings in the future in order to meet our capital needs partly in relation to the construction of our self-built data centers.

In March 2013,August 2017, we issued RMB1 billionUS$200 million in aggregate principal amount of RMB denominated bondsUSD-denominated notes due 2016 with2020 at a coupon rate of 7.875%7.000% per annum, or the 2016 Bonds, which have been fully repaid by us on March 21, 2016.Original Notes. In June 2014,September 2017, we issued RMB2 billionUS$100 million in aggregate principal amount of RMB denominated bondsUSD-denominated notes due 20172020 at an interesta coupon rate of 6.875%7.000% per annum, or the 2017 Bonds,Notes. The Notes were priced at a slight premium of 100.04, with an effective yield of 6.98%. The Notes constitute a further issuance of, and usedwere consolidated to form a portion ofsingle series with, the proceedsOriginal Notes. The Original Notes and the Notes are collectively referred to purchase, pursuant to a tender offer, substantially allas the 2016 Bonds, with only RMB264.3 million of the principal amount of the 2016 Bonds outstanding as of December 31, 2014 and December 31, 2015. Subsequently, remaining principal of 2016 Bonds and related interests were paid off in March 2016.“2020 Notes”. Interest on the 2017 Bonds2020 Notes is payable semi-annually in arrears on, or nearest to, June 26August 17 and December 26February 17 in each year, beginning on December 26, 2014.February 17, 2018. The 2017 Bonds2020 Notes have restrictive covenants relating to financial ratios as well as our capital raising activities and other financial and operational matters, which may make it more difficult for us to obtain additional capital and to pursue business opportunities, including potential acquisitions. Such covenants restrict our abilities to declare dividends or incur or guarantee additional indebtedness, among other things. See “Item 5. Operating and Financial Review and Prospects—B. Liquidity and Capital Resources” for more detailed information on restrictive covenants of the 2017 Bonds.

In October 2013, we issued 34,683,042 Class A ordinary shares (in the form of 5,780,507 ADSs) to Esta Investments Pte Ltd, or Esta, for an aggregate cash consideration of US$86.7 million. In addition, Esta purchased 5,316,960 Class A ordinary shares (in the form of 886,160 ADSs) from certain of our existing shareholders for a total cash consideration of US$13.3 million which was paid to the selling shareholders through us.2020 Notes.

In January 2015, we issued (i) 39,087,125 Class A and 18,250,268 Class B ordinary shares to King Venture Holdings Limited, or Kingsoft, for an aggregate cash consideration of US$172 million; (ii) 6,142,410 Class A and 10,524,257 Class B ordinary shares to Xiaomi Ventures Limited, or Xiaomi, for an aggregate cash consideration of US$50 million; and (iii) 24,668,022 Class A ordinary shares (in the form of 4,111,337 ADSs) to Esta, for an aggregate cash consideration of US$74 million.

In May 2016, we issued 31,996,874 Class A and 111,053,390 Class B ordinary shares to Tus-Holdings Co., Ltd., or Tus-Holdings, for an aggregate cash consideration of US$388 million.

If we raise additional funds through further issuances of equity or equity-linked securities, our existing shareholders could suffer significant dilution in their percentage ownership of our company, and any new equity securities we issue could have rights, preferences, and privileges senior to those of holders of our ADSs or ordinary shares.

Servicing our debt requires a significant amount of cash, and we may not have sufficient cash flow from our business to pay our debt.

Our ability to make scheduled payments of the principal of, to pay interest on or to refinance our indebtedness, including the 2017 Bonds, depends on our future performance, which is subject to economic, financial, competitive and other factors beyond our control. Our business may not continue to generate cash flow

from operations in the future sufficient to service our debt and make necessary capital expenditures. If we are unable to generate such cash flow, we may be required to adopt one or more alternatives, such as selling assets, restructuring debt or obtaining additional equity capital on terms that may be onerous or highly dilutive. Our ability to refinance our indebtedness will depend on the capital markets and our financial condition at such time. We may not be able to engage in any of these activities or engage in these activities on desirable terms, which could result in a default on our debt obligations.

As of December 31, 2015,2017, our total consolidated indebtedness and other liabilities representing total bank borrowings, bonds payables, accounts and notes payable and accrued expenses and other payables and mandatorily redeemable noncontrolling interests were RMB3,903.1RMB3,147.2 million (US$602.5483.7 million). Failure to servicing our debt would constitute an event of default under the terms of the bonds, which would have a material adverse effect on our financial condition and results of operations.

Occurrence of any change of control could cause us to make an offer to repurchase the 2017 Bonds.

Under the terms of the 2017 Bonds, at any time following the occurrence of a change of control event, we will be required to make an offer to repurchase all or, at the bondholder’s option, any part (equal to RMB1,000,000 or multiples of RMB100,000 in excess thereof), of each bondholder’s bonds at 101% of the aggregate principal amount of the bonds repurchased plus accrued and unpaid interest, if any, on the bonds repurchased. If such a change of control event were to occur, we may not have sufficient cash and may not be able to arrange financing to redeem the bonds in time, or on acceptable terms, or at all. Failure to repay, repurchase or redeem tendered bonds by us would constitute an event of default under the bonds, which would have a material adverse effect on our financial condition and results of operations.

If we are unable to comply with the restrictions and covenants contained in our debt agreements, an event of default could occur under the terms of such agreements, which could cause repayment of such debt to be accelerated.

If we are unable to comply with the restrictions and covenants in our current or future debt and other agreements, there could be a default under the terms of these agreements. In the event of a default under these agreements, the holders of the debt could terminate their commitments to lend to us, accelerate the debt and declare all amounts borrowed due and payable or terminate the agreements, whichever the case may be.

Furthermore, some of our debt agreements including the 2017 Bonds, may contain cross-acceleration or cross-default provisions. As a result, our default under one debt agreement may cause the acceleration of debt including the 2017 Bonds, or result in a default under our other debt agreements, including the 2017 Bonds.agreements. If any of these events occur, we cannot assure you that our assets and cash flow would be sufficient to repay in full all of our indebtedness, or that we would be able to find alternative financing. Even if we could obtain alternative financing, we cannot assure you that it would be on terms that are favorable or acceptable to us.

Increased power costs and limited availability of electrical resources maycould adversely affect our results of operations.

Costs of power account for a significant portion of our overall costs for both our self-built data centers and partnered data centers. We may not be able to pass on increased power costs to our customers, which could harm our results of operations. Power and cooling requirements at our data centers are also increasing as a result of the increasing power demands of today’s servers. Since we rely on third parties to provide our data centers with power, our data centers could have a limited or inadequate access to power. Our customers’ demand for power may also exceed the power capacity in our older data centers, which may limit our ability to fully utilize these data centers. This could adversely affect our relationships with our customers, which could harm our business and have an adverse effect on our results of operations.

If we are unable to manage our growth effectively, our financial results could suffer.

The growth of our business and our service offerings may strain our operating and financial resources. Furthermore, we intend to continue expanding our overall business, customer base, headcount, and operations. Managing a geographically dispersed workforce requires substantial management effort and significant additional investment in our operating and financial system capabilities and controls. If our information systems are unable to support the demands placed on them by our growth, we may need to implement new systems, which would be disruptive to our business. We may also initiate similar network upgrade in the future if required by our operations. We may be unable to manage our expenses effectively in the future due to the expenses associated with these expansions and such expansions or upgrade may cause disruption of services to our customers, which may negatively impact our net revenues and operating expenses. If we fail to improve our operational systems or to expand our customer service capabilities to keep pace with the growth of our business, we could experience customer dissatisfaction, cost inefficiencies, and lost revenue opportunities, which may materially and adversely affect our results of operations.

If we are unable to successfully identify and analyze changing market trends and adjust our growth strategies accordingly in a timely and cost-effective manner, our results of operations could be adversely affected.

As China’s internet infrastructure market remains at its early stage, especially compared to those in more advanced economies, we generally operate in a more complex business environment with changing market dynamics. On one hand, the imbalance between material growth in internet traffic and the relative limited supply of high quality internet infrastructure services drives strong demand for not only data center services, but also complementary value-added services in adjacent markets, including interconnectivity services, network transmission services CDN services,and cloud services, VPN services and last-mile wired broadband services among others. On the other hand, the potential changes in competitive landscape and regulations in an otherwise highly regulated market continues to present ambiguities and challenges. Therefore, we need to evaluate, on a continuously basis, the changing market dynamics and from time to time make adjustments to our growth strategies and operations accordingly. Any material changes to our strategies and operations, including adjustments to business models, new business areas and acquisitions, are evaluated financially, strategically and operationally by the management and approved by our board of directors. In 2017, after thorough evaluation by the management and approval by the board, we completed the disposal of our managed network services business segment, including CDN services, hosting area network services, route optimization and last-mile broadband businesses, as these businesses were loss-making due to the intense market competition. However, if we fail to capture new growth opportunities, or become unsuccessful in modifying our strategies and operations to adapt to these changing market conditions in a timely and cost-effective manner, our results of operations could be materially and adversely affected.

In addition, we have and may continue to expand in new business areas that we believe either strengthen our competitive position or will improve our future growth rates. Some of these new business areas require substantial upfront investments, which may precede anticipated generation of revenues. For example, as large-scale cloud service providers have increasing demands for customized data centers, we are planning to provide wholesale data center services for them. If we fail to successfully manage the progress of these new growth initiatives, or if changing market conditions prove to work against our proposed business plans, or if we fail to compete effectively with other market players, we may not be able to attract new customers and generate general revenues and profits as anticipated, which couldmay materially and adversely affect our results of operations.business expansion.

If we are unable to adapt to evolving technologies and customer demands in a timely and cost-effective manner, our ability to sustain and grow our business may suffer.

To be successful, we must adapt to our rapidly changing market by continually improving the performance, features, and reliability of our services and modifying our business strategies accordingly. We could also incur substantial costs if we need to modify our services or infrastructure in order to adapt to these changes. We may not be able to timely adapt to changing technologies, if at all. Our ability to sustain and grow our business would

suffer if we fail to respond to these changes in a timely and cost-effective manner. New technologies or industry standards have the potential to replace or provide lower cost alternatives to our data center services. The adoption of such new technologies or industry standards could render some or all of our services obsolete or unmarketable. We cannot guarantee that we will be able to identify the emergence of all of these new service alternatives successfully, modify our services accordingly, or develop and bring new products and services to market in a

timely and cost-effective manner to address these changes. If and when we do identify the emergence of new service alternatives and introduce new products and services to market, those new products and services may need to be made available at lower price points than our then-current services. Failure to provide services to compete with new technologies or the obsolescence of our services could lead us to lose current and potential customers or could cause us to incur substantial costs, which would harm our results of operations and financial condition. Our introduction of new alternative products and services that have lower price points than current offerings may result in our existing customers switching to the lower cost products, which could reduce our revenues and have a material adverse effect of our results of operations.

We have expanded to the cloud services market for a short period of time and failure to successfully grow our cloud service business will have a material and adverse effect on our growth, results of operations and business prospects.

Through our strategic partnership with Microsoft, we started providing public cloud service in 2013 and hybrid cloud service in 2014. We further expanded to provide private cloud and hybrid services through our partnership with IBM in 2014. In October 2016, we launched IBM Bluemix cloud services which are now generally available in China. Cloud services are a new and emerging market in China and we have limited experience in this market. Our success in the cloud service business is subject to various risks and uncertainties, including:

If we are unable to effectively manage these risks, we may not be able to successfully operate in the cloud services market and achieve the expected growth.

In addition, the expansion into the cloud services market has resulted in a change to our business, including, among others, the change of our customer base. The number of enterprise and government entity customers has increased with our expansion into the cloud services market. Our lack of experience in dealing with enterprise and government entity customers may pose new challenges for us. We may not be able to manage our business growth strategy as planned and our results of operations and business prospects may be materially and adversely affected.

If we fail to maintain a strong brand name, we may lose our existing customers and have difficulties attracting new customers, which may have an adverse effect on our business and results of operation.

We have built a strong brand in Chinese, “ ”, among our customers. As our business grows, we plan to continue to focus our efforts to establish a wider recognition of our brand to attract potential customers. We

cannot assure you that we will effectively allocate our resources for these activities or succeed in maintaining and broadening our brand recognition among customers. Our major brand names and logos are registered trademarks in China. However, preventing trademark and trade name infringement or misuse could be difficult, costly and time-consuming, particularly in China. There had been incidents in the past where third parties used our brand without our authorization and we had to resort to litigation to protect our intellectual property rights. See “Item 8.A—Legal Proceedings” for our disputes with Shanghai 21Vianet Information Systems Co., Ltd. We may continue to experience similar disputes in the future or otherwise fail to fully protect our brand name, which may have an adverse effect on our business and financial results.

Any negative publicity and allegations against us may adversely affect our brand, public image and reputation, which may harm our ability to attract and retain users and business partners and result in material adverse impact on our business, results of operations and prospects.

Negative publicity and allegations about us, our products and services, our financial results or our market position in general, including by short sellers or investment research firms, regardless of their veracity, may adversely damage our brand, public image and reputation, harm our ability to attract and retain users and result in material adverse impact on our share price, business, results of operations and prospects. For example, on September 10, 2014, Trinity Research Group, or Trinity, a short seller that was allegedly formed in 2014, issued a report alleging that we operate through a Ponzi scheme and have reported fraudulent financials and operating metrics. On September 17, 2014, Trinity issued a second report. The trading price of our ADSs declined and two shareholder class action lawsuits were filed against us and some of our directors and senior executive officers. See “Item 8.A—Legal Proceedings” for more information on the two shareholder class action lawsuits. Through two separate, comprehensive rebuttal reports, we have rejected all the allegations set out in the Trinity reports and are prepared to defend ourselves in the shareholder class action lawsuits, but our share price fluctuated after such negative publicity.

Rapid urbanization and changes in zoning and urban planning in China may cause our leased properties to be demolished, removed or otherwise affected.

China is undergoing a rapid urbanization process, and zoning requirements and other governmental mandates with respect to urban planning of a particular area may change from time to time. When there is a change in zoning requirements or other governmental mandates with respect to the areas where our data centers are located, the affected data centers may need to be demolished and removed. As a result, we may have to relocate our data centers to other locations. We have not experienced such demolition and relocation in the past, but we cannot assure you that we will not experience demolitions or interruptions of our data center operations due to zoning or other local regulations. Any such demolition and relocation could cause us to lose primary locations for our data centers and we may not be able to achieve comparable operation results following the relocations. While we may be reimbursed for such demolition and relocation, we cannot assure you that the reimbursement, as determined by the relevant government authorities, will be sufficient to cover our direct and indirect losses. Accordingly, our business, results of operations and financial condition may be materially and adversely affected.

Our senior management has worked together for a relatively short period of time, which may make it difficult for you to evaluate their effectiveness and ability to address challenges.

Due to recent changes to our management team, certain of our senior management and employees have worked together at our company for a relatively short period of time. For example, we have recently experienced turnover in our senior management ranks and hired or appointed a number of executive officers and senior management, in 2015, including our chiefco-chief executive officer and president and chief financial officer. In light of the foregoing circumstances, it may be difficult for you to evaluate the effectiveness of our senior management and their ability to address future challenges to our business. Members of our senior management may not work together effectively as a team to manage our growth successfully, which may expose us to a higher risk of internal control deficiencies and result in us losing market share, business opportunity and revenues.

Our business depends substantially on the continuing efforts of our executives, and our business may be severely disrupted if we lose their services.

Our future success heavily depends upon the continued services of our executives and other key employees. In particular, we rely on the expertise and experience of Sheng Chen, ourco-founder and executive chairman of the board of directors. We rely on their industry expertise, their experience in our business operations and sales and marketing, and their working relationships with our employees, our other major shareholders, our clients and

relevant government authorities. If one or more of our senior executives were unable or unwilling to continue in their present positions, we might not be able to replace them easily or at all. If any of our senior executives joins a competitor or forms a competing company, we may lose clients, suppliers, key professionals and staff members. Each of our executive officers has entered into an employment agreement with us, which containsnon-competition provisions. However, if any dispute arises between our executive officers and us, we cannot assure you the extent to which any of these agreements could be enforced in China, where these executive officers reside, in light of the uncertainties with China’s legal system. See “—Risks Related to Doing Business in China—Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.”

If we are unable to recruit or retain qualified personnel, our business could be harmed.

We must continue to identify, hire, train, and retain IT professionals, technical engineers, operations employees, and sales and management personnel who maintain relationships with our customers and who can provide the technical, strategic, and marketing skills required for our company to grow. There is a shortage of qualified personnel in these fields, and we compete with other companies for the limited pool of these personnel. Any failure to recruit and retain necessary technical, managerial, sales, and marketing personnel, including but not limited to members of our executive team, could harm our business and our ability to grow.

Our managed network services businessThe benefits from our partnership with Warburg Pincus may fluctuate or decline.take longer than expected to realize, if at all.

Although managed network services are oneIn March 2017, we signed an investment agreement with Warburg Pincus to establish a multi-stage joint venture and build a digital real estate platform in China. The cooperation will allow us to reduce our capital expenditures in the future as Warburg Pincus will take primary responsibilities to build new wholesale data centers. However, the success of our core competenciespartnership is dependent on the ability of the joint venture to source new projects and deals. There is no guarantee that the joint venture will be able to source new projects, find appropriate project financing, negotiate favorable terms with the counterparties, adhere to scheduled timelines for project completion, or navigate the Chinese real-estate market efficiently. In addition, there may be delays in our overall service offerings as a comprehensive infrastructure provider in China, our managed network service business has been and will likely remain a relatively more volatile portioncompletion of current projects, caused by construction delays, budget overtures, prolonged negotiations with suppliers, contractors or government entities, among other things. The failure of our overall revenue base. As the managed network services market continuescooperation with Warburg Pincus to evolvecarry out new and ascurrent projects will cause us to continue making capital expenditures to maintain our growth. Furthermore, we further optimize our growth strategies and allocate resourcescannot assure you that we will be able to more attractive areas with higher growth and return rates, we may become more selective in pursuing future revenue opportunitiescontinuously lease data center spaces from Warburg Pincus at a commercially reasonable price in the managed network services business. In addition,future, and it may lease its data centers to our competitors in its sole discretion. If we have experienced pricing pressure forfail to maintain a good relationship with Warburg Pincus or extend our managed network services in recent yearspartnership after the expiration of the investment agreement, our results of operations could be materially and we expect that this trend may continue. Therefore, revenues from managed network services could experience decline both in the absolute amount and as a percentage of our consolidated revenues, which could have a negative impact on our overall growth and profitability.adversely affected.

The uncertain economic environment may continue to have an adverse impact on our business and financial condition.

The uncertain economic environment could have an adverse effect on our liquidity. While we believe we have a strong customer base, if the current market conditions were to worsen, some of our customers may have difficulty paying us and we may experience increased churn in our customer base and reductions in their commitments to us. AsFor example, we had a long outstanding receivable from a state-owned enterprise client. We made a full allowance for doubtful debt, even though we still have an opportunity to collect a portion of the date of this annual report,receivable in the future. Although we have not experienced any of the foregoing; however,believe it to be aone-time expense, if thesesimilar circumstances do occur to other customers, we may be required to further increase our allowance for doubtful accountsdebt and our results would be negatively impacted. Our sales cycle could also be lengthened if customers slow spending, or delay decision-making, on our products and services, which could adversely affect our revenues growth and our ability to recognize revenue. Finally, we could also experience pricing pressure as a result of economic conditions if our competitors lower prices and attempt to lure away our customers with lower cost solutions. Finally, our ability to access the capital markets may be severely restricted at a time when we would like, or need, to do so which could have an impact on our flexibility to pursue additional expansion opportunities and maintain our desired level of revenue growth in the future.

Our results of operations have fluctuated and may continue to fluctuate, which could make our future results difficult to predict. This may also result in significant volatility in, and otherwise adversely affect, the market for our ADSs.

Our results of operations have fluctuated and may continue to fluctuate due to a variety of factors, including many of the risks described in this section, which are outside of our control. As a result, comparing our results of operations on aperiod-to-period basis may not be meaningful. You should not rely on our results of operations for any prior periods as an indication of our future operating performance. Fluctuations in our revenue can lead to even greater fluctuations in our results of operations. Our budgeted expense levels depend in part on our expectations of long-term future revenue. Given relatively fixed operating costs related to our personnel and facilities, any substantial adjustment to our expenses to account for lower than expected levels of revenue will be difficult and time consuming. Consequently, if our revenues do not meet projected levels, our operating performance will be negatively affected. Fluctuations in our results of operations could result in significant volatility in, and otherwise adversely affect, the market for our ADSs.

If we fail to maintain an effective system of internal control over financial reporting, we may be unable to accurately report our financial results or prevent fraud, and investor confidence in our company and the market price of our ADSs may be adversely affected.

The SEC, as required by Section 404 of the Sarbanes-Oxley Act of 2002, or the Sarbanes-Oxley Act, adopted rules requiring most public companies to include a management report on such company’s internal control over financial reporting in its annual report, which contains management’s assessment of the effectiveness of the company’s internal control over financial reporting. In addition, when a company meets the SEC’s criteria, an independent registered public accounting firm must report on the effectiveness of the company’s internal control over financial reporting.

Our management and independent registered public accounting firm have concluded that our internal control over financial reporting as of December 31, 20152017 was effective. However, we cannot assure you that in the future our management or our independent registered public accounting firm will not identify material weaknesses during the Section 404 of the Sarbanes-Oxley Act audit process or for other reasons. In addition, because of the inherent limitations of internal control over financial reporting, including the possibility of collusion or improper management override of controls, material misstatements due to error or fraud may not be prevented or detected on a timely basis. As a result, if we fail to maintain effective internal control over financial reporting or should we be unable to prevent or detect material misstatements due to error or fraud on a timely basis, investors could lose confidence in the reliability of our financial statements, which in turn could harm our business, results of operations and negatively impact the market price of our ADSs, and harm our reputation. Furthermore, we have incurred and expect to continue to incur considerable costs and to use significant management time and other resources in an effort to comply with Section 404 and other requirements of the Sarbanes-Oxley Act.

Compliance with rules and regulations applicable to companies publicly listed in the United States is costly and complex and any failure by us to comply with these requirements on an ongoing basis could negatively affect investor confidence in us and cause the market price of our ADSs to decrease.

In addition to Section 404, the Sarbanes-Oxley Act also mandates, among other things, that companies adopt corporate governance measures, imposes comprehensive reporting and disclosure requirements, sets strict independence and financial expertise standards for audit committee members, and imposes civil and criminal penalties for companies, their chief executive officers, chief financial officers and directors for securities law violations. For example, in response to the Sarbanes-Oxley Act, NASDAQ has adopted additional comprehensive rules and regulations relating to corporate governance. These laws, rules and regulations have increased the scope, complexity and cost of our corporate governance and reporting and disclosure practices. Our current and future compliance efforts will continue to require significant management attention. In addition, our

board members, chief executive officer and chief financial officer could face an increased risk of personal

liability in connection with the performance of their duties. As a result, we may have difficulty attracting and retaining qualified board members and executive officers to fill critical positions within our company. Any failure by us to comply with these requirements on an ongoing basis could negatively affect investor confidence in us, cause the market price of our ADSs to decrease or even result in the delisting of our ADSs from NASDAQ.

We are subject to China’s anti-corruption laws and the U.S. Foreign Corrupt Practices Act. Our failure to comply with these laws could result in penalties, which could harm our reputation and have an adverse effect on our business, results of operations and financial condition.

We are subject to the U.S. Foreign Corrupt Practices Act, or the FCPA, which generally prohibits companies and anyone acting on their behalf from offering or making improper payments or providing benefits to foreign officials for the purpose of obtaining or keeping business, along with various other anti-corruption laws, including China’s anti-corruption laws. Our existing policies prohibit any such conduct and we are in the process of implementing additional policies and procedures designed to ensure that we, our employees and intermediaries comply with the FCPA and other anti-corruption laws to which we are subject. There is, however, no assurance that such policies or procedures will work effectively all the time or protect us against liability under the FCPA or other anti-corruption laws for actions taken by our employees and intermediaries with respect to our business or any businesses that we may acquire. We operate in the data center services industry in China and generally purchase our hosting facilities and telecommunications resources from state or government-owned enterprises and sell our services domestically to customers that include state or government-owned enterprises or government ministries, departments and agencies. This puts us in frequent contact with persons who may be considered “foreign officials” under the FCPA, resulting in an elevated risk of potential FCPA violations. If we are found to be not in compliance with the FCPA and other applicable anti-corruption laws governing the conduct of business with government entities or officials, we may be subject to criminal and civil penalties and other remedial measures, which could have an adverse impact on our business, financial condition and results of operations. Any investigation of any potential violations of the FCPA or other anti-corruption laws by U.S. or foreign authorities, including Chinese authorities, could adversely impact our reputation, cause us to lose customer sales and access to hosting facilities and telecommunications resources, and lead to other adverse impacts on our business, financial condition and results of operations.

If we fail to maintain a strong brand name, we may lose our existing customers and have difficulties attracting new customers, which may have an adverse effect on our business and results of operation.

We have built a strong brand in Chinese, “ “, among our customers. As our business grows or changes, we plan to continue to focus our efforts to establish a wider recognition of our brand to attract potential customers, and we may also introduce additional brands in relation to our business. We cannot assure you that we will effectively allocate our resources for these activities or succeed in maintaining and broadening our brand recognition among customers. Our major brand names and logos are registered trademarks in China. However, preventing trademark and trade name infringement or misuse could be difficult, costly and time-consuming, particularly in China. There had been incidents in the past where third parties used our brand without our authorization and we had to resort to litigation to protect our intellectual property rights. See “Item 8.A—Legal Proceedings” for our disputes with Shanghai 21Vianet Information Systems Co., Ltd. We may continue to experience similar disputes in the future or otherwise fail to fully protect our brand name, which may have an adverse effect on our business and financial results.

If we fail to protect our intellectual property rights in general, our business may suffer.

We consider our copyrights, trademarks, trade names and internet domain names invaluable to our ability to continue to develop and enhance our brand recognition. Historically, the PRC has afforded less protection to intellectual property rights than the United States. We utilize proprietaryknow-how and trade secrets and employ various methods to protect such intellectual property. Unauthorized use of our copyrights, trademarks, trade names and domain names may damage our reputation and brand. Preventing copyright, trademark and trade

name infringement or misuse could be difficult, costly and time-consuming, particularly in China. The measures we take to protect our copyrights, trademarks and other intellectual property rights are currently based upon a combination of trademark and copyright laws in China and may not be adequate to prevent unauthorized uses. Furthermore, application of laws governing intellectual property rights in China is uncertain and evolving, and could involve substantial risks to us. If we are unable to adequately protect our trademarks, copyrights and other intellectual property rights in the future, we may lose these rights, our brand name may be harmed, and our business may suffer materially. Furthermore, our management’s attention may be diverted by violations of our intellectual property rights, and we may be required to enter into costly litigation to protect our proprietary rights against any infringement or violation.

We may face intellectual property infringement claims that could be time-consuming and costly to defend. If we fail to defend ourselves against such claims, we may lose significant intellectual property rights and may be unable to continue providing our existing services.

Our technologies and business methods, including those relating to data center services, may be subject to third-party claims or rights that limit or prevent their use. Companies, organizations or individuals, including our competitors, may hold or obtain patents or other proprietary rights that would prevent, limit or interfere with our ability to make, use or sell our services or develop new services, which could make it more difficult for us to operate our business. Intellectual property registrations or applications by others relating to the type of services that we provide may give rise to potential infringement claims against us. In addition, to the extent that we gain greater visibility and market exposure as a public company, we are likely to face a higher risk of being subject to intellectual property infringement claims from third parties. We expect that infringement claims may further increase as the number of products, services and competitors in our market increases. Further, continued success in this market may provide an impetus to those who might use intellectual property litigation as a tool against us.

It is critical that we use and develop our technology and services without infringing the intellectual property rights of third parties, including but not limited to patents, copyrights, trade secrets and trademarks. Intellectual property litigation is expensive and time-consuming and could divert management’s attention from our business. A successful infringement claim against us, whether with or without merit, could, among others things, require us to pay substantial damages, developnon-infringing technology or enter into royalty or license agreements that may not be available on acceptable terms, if at all, and cease making, licensing or using products that have infringed a third party’s intellectual property rights. Protracted litigation could also result in existing or potential customers deferring or limiting their purchase or use of our products until resolution of such litigation, or could require us to indemnify our customers against infringement claims in certain instances. Any intellectual property litigation could have a material adverse effect on our business, results of operations or financial condition.

If we fail to defend ourselves against any intellectual property infringement claim, we may lose significant intellectual property rights and may be unable to continue providing our existing services, which could have a material adverse effect on our results of operations and business prospects.

We have granted, and may continue to grant, stock options and other forms of share-based incentive awards, which may result in significant share-based compensation expenses.

As of the date of this annual report,March 31, 2018, options to purchase 3,591,6121,396,488 ordinary shares and 3,784,2581,529,787 RSUs, have been granted under our 2010 share incentive plan, or the 2010 Plan, and 2014 share incentive plan, or the 2014 Plan. See “Item 6.B—Compensation of Directors and Executive Officers—Share Incentive Plans.” For the year ended December 31, 2015,2017, we recorded RMB190.0RMB47.1 million (US$29.37.2 million) in share-based compensation expenses.

We believe share-based incentive awards enhance our ability to attract and retain key personnel and employees, and we will continue to grant stock options, RSUs and other share-based awards to employees in the future. If our share-based compensation expenses continue to be significant, our results of operations would be materially and adversely affected.

Furthermore, in 2010, we recorded RMB206.1 million of share-based compensation expenses in connection with 24,826,090 fully-vested ordinary shares issued to Sunrise Corporate Holding Ltd., or Sunrise, a company solely owned by our executive chairman. Subsequently, in July 2012, we repurchased 2,686,965 shares from Sunrise at par value, for the purpose of increasing the maximum aggregate number of shares available for grant under our 2010 Plan by the same amount. We may record share-based compensation expense for a portion or all of the shares that are held by Sunrise or the shares that were added to our 2010 Plan, as amended, again at significantly different values if our executive chairman decides at a future date to transfer a portion of these shares to existing and former employees of our company.

Any share-based shareholder contribution, if and when

made by our executive chairman for the benefit of our company, would be required to be recognized as share-based compensation expenses within our results of operations, which would be derived from the estimated fair value of the ordinary share award on the transfer date. Our future results of operations may be materially and adversely affected if a significant amount of share-based compensation is recorded in connection with such future transfers of these ordinary shares.

We may not have adequate insurance coverage to protect us from potential losses.

Our operations are subject to hazards and risks normally associated with daily operations for our data centers. Currently, we maintain insurance policies for our equipment, but we do not maintain any business interruption insurance or third-party liability insurance. The insurance policies for our equipment may only be sufficient to cover a portion of the total value of all equipment in the event that losses occur. Insurance companies in China currently do not offer as extensive an array of insurance products as insurance companies do in more developed economies. The occurrence of any events not covered by our limited insurance coverage may result in interruption of our operations and subject us to significant losses or liabilities. In addition, any losses or liabilities that are not covered by our current insurance policies or are not insured at all may have a material adverse effect on our business, results of operations and financial condition.

We face risks related to natural disasters, health epidemics and other outbreaks, which could significantly disrupt our operations.

On May 12, 2008 and April 14, 2010, severe earthquakes hit part of Sichuan province in southeastern China and part of Qinghai province in western China, respectively, resulting in significant casualties and property damage.

While we did not suffer any loss or experience any significant increase in cost resulting from these earthquakes, ifIf a similarnature disaster were to occur in the future that affected Beijing or another city where we have major operations, our operations could be materially and adversely affected due to loss of personnel and damages to property. In addition, a similarnatural disaster affecting a larger, more developed area could also cause an increase in our costs resulting from the efforts to resurvey the affected area. Even if we are not directly affected, such a disaster could affect the operations or financial condition of our customers and suppliers, which could harm our results of operations.

In addition, our business could be materially and adversely affected by natural disasters or public health emergencies, such as the outbreak of avian influenza, severe acute respiratory syndrome, or SARS, the influenza A (H1N1) virus, Ebola virus, or another epidemic. Any outbreak of avian flu, SARS, H1N1, or their variations, or other adverse public health epidemic in China may have a material and adverse effect on our business operations. These occurrences could require the temporary closure of our offices or prevent our staff from traveling to our customers’ offices to provideon-site services. Such closures could severely disrupt our business operations and adversely affect our results of operations.

Our independent registered public accounting firm, like other independent registered public accounting firms operating in China, is not permitted to be subject to inspection by the Public Company Accounting Oversight Board and, as such, you are deprived of the benefits of such inspection.

Our independent registered public accounting firm that issues the audit reports included in our annual reports filed with the U.S. Securities and Exchange Commission, or SEC, as auditors of companies that are traded publicly in the United States and a firm registered with the U.S. Public Company Accounting Oversight Board (United States), or the PCAOB, is required by the laws of the United States to undergo regular inspections by the PCAOB to assess its compliance with the laws of the United States and professional standards. Because our auditors are located in the People’s Republic of China, a jurisdiction where the PCAOB is currently unable to conduct inspections without the approval of the Chinese authorities, our auditors, like other independent registered public accounting firms operating in China, are currently not inspected by the PCAOB. In May 2013, PCAOB announced that it had entered into a Memorandum of Understanding on

Enforcement Cooperation with the China Securities Regulatory Commission, or the CSRC, and the Ministry of Finance, which establishes a cooperative framework between the parties for the production and exchange of audit documents relevant to investigations undertaken by PCAOB, the China Securities Regulatory Commission, or the CSRC, or the Ministry of Finance in the United States and the PRC,

respectively. PCAOB continues to be in discussions with the CSRC and the Ministry of Finance to permit joint inspections in the PRC of audit firms that are registered with PCAOB and audit Chinese companies that trade on U.S. exchanges.

Inspections of other firms that the PCAOB has conducted outside China have identified deficiencies in those firms’ audit procedures and quality control procedures, which may be addressed as part of the inspection process to improve future audit quality. The inability of the PCAOB to conduct inspections of auditors in China makes it more difficult to evaluate the effectiveness of our auditor’s audit procedures or quality control procedures as compared to auditors outside of China that are subject to PCAOB inspections. Investors may lose confidence in our reported financial information and procedures and the quality of our financial statements, which may have a material adverse effect on our ADS price.

Proceedings instituted recently by the SEC against fivePRC-based accounting firms, including our independent registered public accounting firm, could result in our financial statements being determined to not be in compliance with the requirements of the Exchange Act.

In late 2012, the SEC commenced administrative proceedings under Rule 102(e) of its Rules of Practice and also under the Sarbanes-Oxley Act of 2002 against the Chinese affiliates of the ‘‘big four’’ accounting firms, (including our auditors) and also against Dahua (the former BDO affiliate in China). The Rule 102(e) proceedings initiated by the SEC relate to these firms’ inability to produce documents, including audit work papers, in response to the request of the SEC pursuant to Section 106 of the Sarbanes-Oxley Act of 2002, as the auditors located in the PRC are not in a position lawfully to produce documents directly to the SEC because of restrictions under PRC law and specific directives issued by the China Securities Regulatory Commission. The issues raised by the proceedings are not specific to our auditors or to us, but affect equally all audit firms based in China and all China-based businesses with securities listed in the United States.

In January 2014, the administrative judge reached an initial decision that the “big four” accounting firms should be barred from practicing before the Commission for six months. The “big four” accounting firms appealed the initial administrative law decision to the SEC in February 2014. In February 2015, each of the “big four” accounting firms agreed to a censure and to pay a fine to the SEC to settle the dispute and avoid suspension of their ability to practice before the SEC. The settlement requires the firms to follow detailed procedures to seek to provide the SEC with access to Chinese firms’ audit documents via China Securities Regulatory Commission. If the firms do not follow these procedures, the SEC could impose penalties such as suspensions, or it could restart the administrative proceedings.

In the event that the SEC restarts the administrative proceedings, depending upon the final outcome, listed companies in the United States with major PRC operations may find it difficult or impossible to retain auditors in respect of their operations in the PRC, which could result in financial statements being determined to not be in compliance with the requirements of the Securities Exchange Act of 1934, or Exchange Act, including possible delisting. Moreover, any negative news about the proceedings against these audit firms may cause investor uncertainty regarding China-based, United States-listed companies and the market price of our ADSs may be adversely affected.

If our independent registered public accounting firm were denied, even temporarily, the ability to practice before the SEC and we were unable to timely find another registered public accounting firm to audit and issue an opinion on our financial statements, our financial statements could be determined not to be in compliance with the requirements of the Exchange Act. Such a determination could ultimately lead to the delay or abandonment of this offering, delisting of our ordinary shares from the Nasdaq Global Select Market or deregistration from the SEC, or both, which would substantially reduce or effectively terminate the trading of our ADSs in the United States.

Risks Related to Our Corporate Structure

If the PRC government finds that the arrangements that establish the structure for operating our business do not comply with PRC government restrictions on foreign investment in the telecommunications business or if these regulations or the interpretation of existing regulations change in the future, we could be subject to severe penalties or be forced to relinquish our interests in those operations.

The PRC government regulates telecommunications-related businesses through strict business licensing requirements and other government regulations. These laws and regulations also include limitations on foreign ownership of PRC companies that engage in telecommunications-related businesses. Specifically, foreign investors are not allowed to own more than a 50% equity interest in any PRC company engaging in value-added telecommunications businesses.businesses (except operationale-commerce), and the major foreign investor of a telecommunication business in China must also have experience and a sound track record in providing value-added telecommunications services overseas.

Because we are a Cayman Islands company, we are classified as a foreign enterprise under PRC laws and regulations, and our wholly-owned PRC subsidiaries, 21Vianet Data Center Co., Ltd., or 21Vianet China, Joytone Infotech Co., Ltd., or SZ Zhuoaiyi, and Abitcool (China) Broadband Inc., or aBitCool DG, are foreign-invested enterprises, or FIEs. To comply with PRC laws and regulations, we conduct our business in China through contractual arrangements with our variable interest entities and their shareholders. These contractual arrangements provide us with effective control over our variable interest entities, and enable us to receive substantially all of the economic benefits of our consolidated affiliated entities in consideration for the services provided by our wholly-owned PRC subsidiaries, and have an exclusive option to purchase all of the equity interest in our variable interest entities when permissible under PRC laws. For a description of these contractual arrangements, see “Item 7.B—Related Party Transactions—Contractual Arrangements with Our Variable Interest Entities and Their Shareholders.”

The Ministry of Industry and Information Technology, or the MIIT issued a circular in July 2006 requiring foreign investors to set up an FIE and obtain a value-added telecommunications business operating license, or the VAT License, in order to conduct any value-added telecommunications business in China. Pursuant to this circular, a domestic license holder is prohibited from leasing, transferring or selling the license to foreign investors in any form, and from providing any assistance, including resources, sites or facilities, to foreign investors that conduct value-added telecommunications business in China illegally. Furthermore, the relevant trademarks and domain names that are used in the value-added telecommunications business must be owned by the local license holder or its shareholder. The circular further requires each license holder to have the necessary facilities for its approved business operations and to maintain such facilities in the regions covered by its license. In addition, all value-added telecommunications service providers are required to maintain network and information security in accordance with the standards set forth under relevant PRC regulations. Companies in violation of the circular will be ordered by relevant authorities to take remedial actions within a specific period and licenses may be withdrawn if such remedial actions cannot be completed within the specific period. As of the date of this annual report, we have not been notified by relevant authorities regarding any violation of the circular when conducting our value-added telecommunications business, and it is unclear what impact this circular will have on us or other similarly situated companies as the circular is in the process of being amended.business.

We believe that we comply with the current applicable PRC laws and regulations. Beijing DHHHan Kun Law Firm,Offices, our PRC legal counsel, based on its understanding of the relevant laws and regulations, is of the opinion that each of the contracts composing the contractual arrangements among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders is valid, legally binding and enforceable upon each party of such agreements under PRC laws and regulations, and will not result in any violation of PRC laws or regulations currently in effect. However, as there are substantial uncertainties regarding the interpretation and application of PRC laws and regulations, including the Regulations on Mergers and Acquisitions of Domestic Enterprises by Foreign Investors, or the M&A Rules, the telecommunications circular described above and the Telecommunications Regulations of the People’s Republic of China, or the Telecom Regulations, and the relevant regulatory measures concerning the telecommunications industry, therefore, we cannot assure you that

the PRC government that regulate providers of data center service and other telecommunication services and other participants in the telecommunications industry would agree that our corporate structure or any of the above contractual arrangements comply with PRC

licensing, registration or other regulatory requirements, with existing policies or with requirements or policies that may be adopted in the future. PRC laws and regulations governing the validity of these contractual arrangements are uncertain and the relevant government authorities have broad discretion in interpreting these laws and regulations.

If our corporate and contractual structure is deemed by the MIIT, or other regulators having competent authority, to be illegal, either in whole or in part, we may lose control of our consolidated affiliated entities and have to modify such structure to comply with regulatory requirements. However, we cannot assure you that we can achieve this without material disruption to our business. Further, if our corporate and contractual structure is found to be in violation of any existing or future PRC laws or regulations, the relevant regulatory authorities would have broad discretion in dealing with such violations, including:

Furthermore, in connection with litigation, arbitration or other judicial or dispute resolution proceedings, assets under the name of any of record holder of equity interest in our variable interest entities, including such equity interest, may be put under court custody. As a consequence, we cannot be certain that the equity interest will be disposed pursuant to the contractual arrangement or ownership by the record holder of the equity interest. In addition, new PRC laws, rules and regulations may be introduced to impose additional requirements that may be applicable to our corporate structure and contractual arrangements. Occurrence of any of these events could materially and adversely affect our business, financial condition and results of operations. In addition, if the imposition of any of these penalties or requirement to restructure our corporate structure causes us to lose the rights to direct the activities of our variable interest entities or our right to receive their economic benefits, we would no longer be able to consolidate such variable interest entities. However, we do not believe that such actions would result in the liquidation or dissolution of our company, our wholly-owned subsidiaries in China or our variable interest entities or their subsidiaries. For the years ended December 31, 2013, 20142015, 2016 and 2015,2017, our consolidated affiliated entities contributed most of our total net revenues.

Our contractual arrangements with our variable interest entities may result in adverse tax consequences to us.

We could face material and adverse tax consequences if the PRC tax authorities determine that our contractual arrangements with our variable interest entities were not made on an arm’s length basis and may adjust our income and expenses for PRC tax purposes by requiring a transfer pricing adjustment. A transfer pricing adjustment could adversely affect us by (i) increasing the tax liabilities of our variable interest entities without reducing their respective tax liability, which could further result in late payment fees and other penalties to our variable interest entities for underpaid taxes; or (ii) limiting the ability of our variable interest entities to obtain or maintain preferential tax treatments and other financial incentives.

We rely on contractual arrangements with our variable interest entities and their shareholders for our China operations, which may not be as effective as direct ownership in providing operational control.

We rely on contractual arrangements with our variable interest entities and their shareholders to operate our business in China. For a description of these contractual arrangements, see “Item 7.B—Related Party Transactions—Contractual Arrangements with Our Variable Interest Entities and Their Shareholders.” Most of our revenues are attributed to our consolidated affiliated entities. These contractual arrangements may not be as effective as direct ownership in providing us with control over our variable interest entities. If our variable interest entities or their shareholders fail to perform their respective obligations under these contractual arrangements, our recourse to the assets held by our consolidated affiliated entities is indirect and we may have to incur substantial costs and expend significant resources to enforce such arrangements in reliance on legal remedies under PRC law. These remedies may not always be effective, particularly in light of uncertainties in the PRC legal system.

All of these contractual arrangements are governed by PRC law and provide for the resolution of disputes through arbitration in the PRC. Accordingly, these contracts would be interpreted in accordance with PRC laws and any disputes would be resolved in accordance with PRC legal procedures. The legal environment in the PRC is not as developed as in other jurisdictions, such as the United States. As a result, uncertainties in the PRC legal system could limit our ability to enforce these contractual arrangements. In the event that we are unable to enforce these contractual arrangements, or if we suffer significant time delays or other obstacles in the process of enforcing these contractual arrangements, it would be very difficult to exert effective control over our variable interest entities, and our ability to conduct our business and our financial conditions and results of operation may be materially and adversely affected. See “—Risks Related to Doing Business in China—Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.”

The shareholders of our variable interest entities may have potential conflicts of interest with us, which may materially and adversely affect our business and financial condition.

We conduct our operations in China through contractual arrangements among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders and we rely on the shareholders of our variable interest entities to abide by the obligations under such contractual arrangements. In particular, 21Vianet Technology is 70% owned by Mr. Sheng Chen, our executive chairman and 30% owned by Mr. Jun Zhang, ourco-founder. Mr. Sheng Chen and Mr. Jun Zhang are also the ultimate shareholders of our company. The interests of Mr. Sheng Chen and Mr. Jun Zhang as the shareholders of 21Vianet Technology may differ from the interests of our company as a whole, as what is in the best interests of 21Vianet Technology may not be in the best interests of our company. We cannot assure that when conflicts of interest arise, any or all of these individuals will act in the best interests of our company or that conflicts of interest will be resolved in our favor. In addition, these individuals may breach or cause our variable interest entities and their subsidiaries to breach or refuse to renew the existing contractual arrangements with us.

Currently, we do not have arrangements to address potential conflicts of interest the shareholders of 21Vianet Technology may encounter, on one hand, and as a beneficial owner of our company, on the other hand; provided that we could, at all times, exercise our option under the optional share purchase agreement to cause them to transfer all of their equity ownership in 21Vianet Technology to a PRC entity or individual designated by us as permitted by the then applicable PRC laws. In addition, if such conflicts of interest arise, we could also, in the capacity ofattorney-in-fact of the then existing shareholders of 21Vianet Technology as provided under the power of attorney, directly appoint new directors of 21Vianet Technology. We rely on the shareholders of our variable interest entities to comply with the laws of China, which protect contracts and provide that directors and executive officers owe a duty of loyalty to our company and require them to avoid conflicts of interest and not to take advantage of their positions for personal gains, and the laws of the Cayman Islands, which provide that directors have a duty of care and a duty of loyalty to act honestly in good faith with a view to our best interests. However, the legal frameworks of China and Cayman Islands do not provide guidance on resolving conflicts in

the event of a conflict with another corporate governance regime. If we cannot resolve any conflicts of interest or disputes between us and the shareholders of our variable interest entities, we would have to rely on legal proceedings, which could result in disruption of our business and subject us to substantial uncertainty as to the outcome of any such legal proceedings.

Risks Related to Doing Business in China

Adverse changes in political and economic policies of the PRC government could have a material adverse effect on the overall economic growth of China, which could reduce the demand for our services and adversely affect our competitive position.

Most of our operations are conducted in China and most of our sales are made in China. Accordingly, our business, financial condition, results of operations and prospects are affected significantly by economic, political and legal developments in China. The PRC economy differs from the economies of most developed countries in many respects, including the amount of government involvement, the level of development, the growth rate, the control of foreign exchange and allocation of resources. While the PRC economy has grown significantly over the past several decades, the growth has been uneven across different periods, regions and among various economic sectors of China. We cannot assure you that the PRC economy will continue to grow, or that if there is growth, such growth will be steady and uniform, or that if there is a slowdown, such a slowdown will not have a negative effect on our business.

The PRC government exercises significant control over China’s economic growth through various measures, such as allocation of resources, controlling payment of foreign currency-denominated obligations, setting monetary policy and providing preferential treatment to particular industries or companies. Some of these measures benefit the overall PRC economy, but may also have a negative effect on us. For example, our financial condition and results of operations may be adversely affected by governmental control over capital investments or changes in tax regulations that are applicable to us. In addition, it is unclear whether PRC economic policies will be effective in maintaining stable economic growth in the future. Any slowdown in China’s economic growth could lead to reduced demand for our solutions, which could in turn materially and adversely affect our business, financial condition and results of operations.

Uncertainties with respect to the PRC legal system could limit legal protections available to you and us.

We conduct most of our business through our PRC subsidiaries and consolidated affiliated entities in China. Our operations in China are governed by PRC laws and regulations. Our PRC subsidiaries are FIEs and are subject to laws and regulations applicable to foreign investment in China and, in particular, laws applicable to FIEs. The PRC legal system is a civil law system based on written statutes. Unlike the common law system, prior court decisions may be cited for reference but are not binding.

Since late 1970s, the PRC government has been developing a comprehensive system of laws and regulations governing economic matters in general. The overall effect of legislation over the past several decades has significantly enhanced the protections afforded to various forms of foreign investments in China. However, China has not developed a fully integrated legal system, and recently enacted laws and regulations may not sufficiently cover all aspects of economic activities in China. In particular, because these laws and regulations are relatively new, and because of the limited volume of published decisions and their nonbinding nature, the interpretation and enforcement of these laws and regulations involve uncertainties. In addition, the PRC legal system is based in part on government policies and internal rules, some of which may not be published on a timely basis or at all, and some of which may have a retroactive effect. As a result, we may not be aware of our violation of these policies and rules until sometime after the violation. Any administrative and court proceedings in China may be protracted, resulting in substantial costs and diversion of resources and management attention. However, since PRC administrative and court authorities have significant discretion in interpreting and implementing statutory and contractual terms, it may be more difficult to evaluate the outcome of administrative

and court proceedings and the level of legal protection we enjoy than in more developed legal systems. These uncertainties may also impede our ability to enforce the contracts we have entered into. As a result, these uncertainties could materially and adversely affect our business and results of operations.

Substantial uncertainties exist with respect to the enactment timetable, interpretation and implementation of draft PRC Foreign Investment Law and how it may impact the viability of our current corporate structure, corporate governance and business operations.

The Ministry of Commerce, or MOC, published a discussion draft of the proposed Foreign Investment Law in January 2015 aiming to, upon its enactment, replace the trio of existing laws regulating foreign investment in China, namely, the Sino-foreign Equity Joint Venture Enterprise Law, the Sino-foreign Cooperative Joint Venture Enterprise Law and the Wholly Foreign-invested Enterprise Law, together with their implementation rules and ancillary regulations. The draft Foreign Investment Law embodies an expected PRC regulatory trend to rationalize its foreign investment regulatory regime in line with prevailing international practice and the legislative efforts to unify the corporate legal requirements for both foreign and domestic investments. The MOC is currently soliciting comments on this draft and substantial uncertainties exist with respect to its enactment timetable, interpretation and implementation. The draft Foreign Investment Law, if enacted as proposed, may materially impact the viability of our current corporate structure, corporate governance and business operations in many aspects.

Among other things, the draft Foreign Investment Law expands the definition of foreign investment and introduces the principle of “actual control” in determining whether a company should be treated as an FIE. According to the definition set forth in the draft Foreign Investment Law, FIEs refer to enterprises established in China pursuant to PRC law that are solely or partially invested by foreign investors. The draft Foreign Investment Law specifically provides that entities established in China (without direct foreign equity ownership) but “controlled” by foreign investors, through contract or trust for example, will be treated as FIEs. Once an entity falls within the definition of FIE, it may be subject to foreign investment “restrictions” or “prohibitions” set forth in a “negative list” to be separately issued by the State Council later. If an FIE proposes to conduct business in an industry subject to foreign investment “restrictions” in the “negative list,” the FIE must go through a market entry clearance by the MOC before being established. If an FIE proposes to conduct business in an industry subject to foreign investment “prohibitions” in the “negative list,” it must not engage in the business. However, an FIE, during the market entry clearance process, may apply in writing to be treated as a PRC domestic enterprise if its foreign investor(s) is/are ultimately “controlled” by PRC government authorities and its affiliates and/or PRC citizens. In this connection, “control” is broadly defined in the draft law to cover the following summarized categories: (i) holding 50% of more of the voting rights of the subject entity; (ii) holding less than 50% of the voting rights of the subject entity but having the power to secure at least 50% of the seats on the board or other equivalent decision making bodies, or having the voting power to exert material influence on the board, the shareholders’ meeting or other equivalent decision making bodies; or (iii) having the power to exert decisive influence, via contractual or trust arrangements, over the subject entity’s operations, financial matters or other key aspects of business operations.

The “variable interest entity” structure, or VIE structure, has been adopted by manyPRC-based companies, including us, to obtain necessary licenses and permits in the industries that are currently subject to foreign investment restrictions in China. See “—Risks Related to Our Corporate Structure” and Item 4.C—“Organizational Structure.” Under the draft Foreign Investment Law, variable interest entities that are controlled via contractual arrangement would also be deemed as FIEs, if they are ultimately “controlled” by foreign investors. Therefore, for any companies with a VIE structure in an industry category that is on the “negative list,” the VIE structure may be deemed legitimate only if the ultimate controlling person(s) is/are of PRC nationality (either PRC companies or PRC citizens). Conversely, if the actual controlling person(s) is/are of foreign nationalities, then the variable interest entities will be treated as FIEs and any operation in the industry category on the “negative list” without market entry clearance may be considered as illegal. But as for investments in industry categories contained in the negative list through VIE structures established before the Foreign

Investment Law takes effect, there is no specific clause in the draft Foreign Investment Law specifying how these investments will be treated. In accordance with an explanation on the draft Foreign Investment Law issued concurrently by the MOC, the MOC is conducting further research and studying on this matter and will put forward disposition suggestions after soliciting public comments. The MOC solicited comments on the draft Foreign Investment Law and substantial uncertainties exist with respect to its enactment timetable, interpretation and implementation. Moreover, it is uncertain whether the industry of data center and providing value-added telecommunication services, in which our variable interest entities operate, will be subject to the foreign investment restrictions or prohibitions set forth in the “negative list” to be issued. If the enacted version of the Foreign Investment Law and the final “negative list” mandate further actions, such as MOC market entry clearance, to be completed by companies with existing VIE structure like us, we face uncertainties as to whether such clearance can be timely obtained, or at all. Any such development could materially impact the viability of our current corporate structure, corporate governance and business operations in many aspects. In the event that a final version of the Foreign Investment Law is enacted, we will conduct a full analysis of our corporate structure, corporate governance and business operations to assess our conformity with the requirements set forth therein.

The draft Foreign Investment Law, if enacted as proposed, may also materially impact our corporate governance practice and increase our compliance costs. For instance, the draft Foreign Investment Law imposes stringent ad hoc and periodic information reporting requirements on foreign investors and the applicable FIEs. Aside from investment implementation report and investment amendment report that are required at each investment and alteration of investment specifics, an annual report is mandatory, and large foreign investors meeting certain criteria are required to report on a quarterly basis. Any company found to benon-compliant with these information reporting obligations may potentially be subject to fines and/or administrative or criminal liabilities, and the persons directly responsible may be subject to criminal liabilities.

We may rely on dividends paid by our operating subsidiaries to fund cash and financing requirements, and limitations on the ability of our operating subsidiaries to make payments to us could have a material adverse effect on our ability to conduct our business and fund our operations.

We are a holding company and conduct our business primarily through our operating subsidiaries and our consolidated affiliated entities, most of which are limited liability companies established in China. We may rely on dividends paid by our subsidiaries for our cash needs, including the funds necessary to pay dividends and other cash distributions to our shareholders, to service any debt we may incur and to pay our operating expenses. The payment of dividends by entities organized in China is subject to limitations. In particular, regulations in China currently permit payment of dividends only out of accumulated profits as determined in accordance with the PRC accounting standards and regulations. Our PRC subsidiaries are also required to set aside at least 10% of theirafter-tax profit based on PRC accounting standards each year to their generalstatutory reserves until the accumulative amount of such reserves reaches 50% of their registered capital. These reserves are not distributable as cash dividends. Furthermore, any portion of itsafter-tax profits that a subsidiary has allocated to its staff welfare and bonus fund at the discretion of its board of directors is also not distributable as cash dividends. Moreover, if our operating subsidiaries incur any debt on their own behalf in the future, the instruments governing the debt may restrict their ability to pay dividends or make other distributions to us. Any limitation on the ability of our operating subsidiaries, including in particular 21Vianet China, to distribute dividends and other distributions to us could materially and adversely limit our ability to make investments or acquisitions that could be beneficial to our businesses, pay dividends or otherwise fund and conduct our business.

If we fail to acquire, obtain or maintain applicable telecommunications licenses, or are deemed by relevant governmental authorities to be operating outsidewithout full compliance with the terms of our existing license,laws and regulations, our business would be materially and adversely affected.

Pursuant to the Telecommunications Regulations promulgated by the PRC State Council in September 2000 and amended in July 2014 and February 2016, respectively, telecommunications businesses are divided into two categories, namely, (i) “basic telecommunications businesses,” which refers to businesses that provide public

network infrastructure, public data transmission and

basic voice communications services, and (ii) “value-added telecommunications businesses,” which refer to businesses that provide telecommunications and information services through the public network infrastructure. If the value-added telecommunications service covers two or more provinces, autonomous regions or municipalities, such service must be approved by the MIIT and the service provider must obtain a Cross-Regional Value Added Telecommunications Business Operation License, or the Cross-Regional VAT License.

Pursuant to the Cross-Regional VAT License issued to Beijing 21Vianet Broad Band Data Center Co., Ltd., or 21Vianet Beijing by the MIIT on January 17, 2012 (which was updated on April 30, 2015)January 23, 2017) with a term effective until January 17, 2017,23, 2022, 21Vianet Beijing is permitted to carry out its (i) full data center business (including internet resources coordination service) under the first category of “value-added telecommunications business” in Beijing; (ii) data center business (excluding internet resources coordination service) under the first category of “value-added telecommunications business” across ten3 province-level municipalities and 18 cities in China.

Pursuant to the VAT License issued to Langfang Xunchi Computer Data Processing Co., Ltd., or LF Xunchi, by the Hebei Province Communications Administration, LF Xunchi is permitted to carry out its data center business in Langfang and Baoding for the period from April 10, 2013 (which was updated on December 23, 2014) to April 10, 2017.

Pursuant to the VAT License issued to Beijing Chengyishidai Network Technology Co., Ltd., or CYSD, by the Beijing Communications Administration on March 30, 2012 with a term effective until June 21, 2016, CYSD is permitted to carry out its internet access service and information service (excluding fixed-line telephone information service and internet information service) business under the second category of “value-added telecommunications business” in Beijing.

Pursuant to the VAT License issued to Guangzhou Gehua Network Technology and Development Company Limited, or Gehua, by the Guangdong Communications Administration, Gehua is permitted to carry out its internet access service business and information service business (limited to internet service business) under the second category of “value-added telecommunications business” in Guangdong province from March 29, 2013 to December 29, 2016.

Pursuant to the VAT License issued to Beijing Fastweb Network Technology Co., Ltd., or BJ Fastweb, by Beijing Communications Administration on December 10, 2014 with a term effective until December 10, 2019, BJ Fastweb is permitted to carry out its internet access service business under the second category of “value-added telecommunications business” in Beijing.

Pursuant to the Cross-Regional VAT License issued to WiFire BJ by the MIIT on August 23, 2013 (which was updated on May 7, 2015) with a term effective until January 7, 2018, WiFire BJ is permitted to carry out its virtual private networkChina; (iii) VPN services under the first category of “value-added telecommunications business” across 253 province-level municipalities and 2 cities in China. Meanwhile, WiFire BJ also holds a VAT License issued by the Beijing Communications Administration on January 22, 2014 with a term effective until December 12, 2014, and is permitted to carry out itsChina; (iv) internet access businessservice (including website access) under the first category of “value-added telecommunications business” across 13 province-level municipalities and provinces in China; and internet access service (excluding website access) under the first category of “value-added telecommunications business” across 6 province-level municipalities and provinces in China; and (v) domestic multi-party communications services under the second category of “value-added telecommunications business” in Beijing. A renewed VAT License was issued to WiFire BJ on December 31, 2014 with a term effective until December 31, 2019.across China.

Pursuant to the VAT License issued to BJ Yilong by Beijing Communications Administration on October 19, 2010, BJ Yilong is permitted to carry out its information service business (limited to mobile network) under the second category of “value-added telecommunications business” in Beijing. A renewed VAT License was issued to BJ Yilong on May 22, 2014 with a term effective until October 18, 2015 and renewed again on September 9, 2015 with a term effective until September 9, 2020.

Pursuant to the VAT License issued to Guangdong Tianying Information Technology Co., Ltd., or GD Tianying, by Guangdong Communications Administration on September 12, 2014 with a term effective until December 16, 2015, GD Tianying is permitted to carry out its data center business under the first category of “value-added telecommunications business” in Guangdong province. A renewed VAT License was issued to GD Tianying on December 16, 2015 with a term effective until December 16, 2020.

Pursuant to the Cross-Regional VAT License issued to Shenzhen Diyixian CommunicationTelecommunication Co., Ltd., or SZ DYX, by the MIIT on September 18, 2013 with a term effective until July 29, 2018, SZ DYX is permitted to carry out (i) its virtual private networkVPN services under the first category of “value-added telecommunications business” in China; and (ii) call center and information service business (limited to mobile network) under the second category of “value-added telecommunications business” across China.China; (iii) data center business (excluding internet data resources coordination service) under the first category of “value-added telecommunications business”, which covers the service in Beijing, Shanghai and Shenzhen; and (iv) internet access service (including website access) under the first category of “value-added telecommunications business” across 7 province-level municipalities and provinces in China

Pursuant to the Cross-Regional VAT License issued to SC AipuShanghai Blue Cloud Technology Co., Ltd., or SH Blue Cloud, by the MIITShanghai Communications Administration on July 31, 2012October 20, 2017 with a term effective until August 1, 2016, SC AipuOctober 20, 2022, SH Cloud is permitted to carry out call center andthe information service business (limited to mobile network)internet information service) under the second category of “value-added telecommunications business” across 11 cities in China.. In addition, pursuant to the VAT License issued to SH Blue Cloud by the MIIT has also approved SC Aipu to authorize each of its 7 subsidiarieson December 19, 2017 with a term effective until February 15, 2020, SH Cloud is permitted to carry out (i) full data center business (including internet access businessdata resources coordination service) under the secondfirst category of “value-added telecommunications business” across 11 cities in China.

Pursuant to the Cross-Regional VAT License issued to Shanghai Guotong Network Co., Ltd., or SH Guotong, by the MIIT on November 15, 2012, which was renewed on January 20, 2015 with a term effective until January 20, 2020, SH Guotong is permitted to carry out internet access businessBeijing and Shanghai; (ii) CDN service under the secondfirst category of “value-added telecommunications business” across 14 cities in China.Beijing and Shanghai; (iii) VPN services under first category of “value-added telecommunications business” in Beijing and Shanghai; (iv) internet access service under the first category of “value-added telecommunications business” in Beijing and Shanghai.

In connection with our data center services, we provide managed network services that connect our data centers with the telecommunication backbones of China’s major carriers, major non-carriers and ISPs as well as connect servers housed in our data centers. Our managed network services are offered in the form of bandwidth with optimized interconnectivity. Furthermore, weWe have been continuously developing our hosting service and managed network service to better serve our customers, and as a result, we introduce new technologies and services from time to time to support and improve our current business. As of the date of this annual report, there is no clear and express legal definition as to what constitutes a “managed network services,” nor are there laws or regulations in China specifically governing the managed network services or categorizing it as one of the “basic telecommunications businesses” or “value-added telecommunications services.” However, we cannot assure you that PRC governmental authorities will continue to deem our hosting service, managed network service and any of our newly developed technologies, network and services used in our business as a type of value-added

telecommunications business or a business covered under the Cross-Regional VAT License issued to 21Vianet Beijing WiFire BJ,and SZ DYX, SC Aipu and SH Guotong, and the VAT License issued to CYSD, Gehua, LF Xunchi, BJ Yilong, BJ Fastweb, GD Tianying and WiFire BJ.Yilong. Furthermore, we cannot assure yourule out the possibility that PRC legislators or governmental authorities will not promulgate any new laws or regulations or update the current and existing laws and regulations which may clearly define or categorize our managedhosting service and any of our newly developed technologies, network and services used in our business as a type of basic telecommunication business.business, which is not covered by our VAT Licenses. As we expand our networks across China, it is also possible that the MIIT, in the future, may deem our operations to have exceeded the terms of our existing licenses. Further, we cannot assure you that 21Vianet Beijing, CYSD, Gehua, LF Xunchi, WiFire BJ, BJ Yilong, SZ DYX SC Aipu, BJ Fastweb, GD Tianying and SH GuotongBlue Cloud will be able to successfully renew their value added telecommunications business operating licenses upon their expiration, or maintain their annual inspection, ornor can we ensure that we will be able to obtain any other licenses necessary for us to carry out our business, or that our existing licenses will continue to cover all aspects of our operations upon their renewal.

In addition, MIIT initiated a periodical pilot scheme for mobile network resale business by issuing the Notice on Carrying out Pilot Work of Mobile Network Resale Business on May 17, 2013, or the Pilot Work Notice, pursuant to which, the qualified private sector enterprises are encouraged, but not required, to apply to participate in the pilot scheme in mobile network resale business and the pilot scheme only lasts for a short period ending on December 31, 2015. MIIT will, according to the Pilot Work Notice, adjust relevant policies in the future as appropriate based on the result of such pilot scheme. 21Vianet Beijing has voluntarily applied to participate in the pilot scheme and obtained approval on August 18, 2014, with a term expiring on December 31, 2015. Following expiration of the Pilot Work Notice, MIIT did not extend the effective period of the pilot scheme or issue a long-term regulation. The mobile network resale business continues and MIIT issued a guideline on January 6, 2016 to regulate the wholesale price in the mobile network resale business. In January 2018, MIIT published a draft Notice on Official Commercialization of Mobile Network Resale Business, or the Draft Mobile Network Resale Business Notice, to solicit opinions from the public by February 22, 2018. Pursuant to the Draft Mobile Network Resale Business Notice, an approved mobile network resale business operator under the aforementioned pilot scheme must enter into a cooperation contract with a basic telecommunication service provider and apply for the applicable telecommunication business operation license. During the application period, a pilot enterprise may continue to carry out its mobile network resale business. However, if the basic telecommunication service provider terminates its cooperation with the pilot enterprise, or the pilot enterprise fails to obtain the applicable telecommunication business operation license within two years after the Draft Mobile Network Resale Business Notice becomes effective, the pilot enterprise must terminate its mobile network resale business. We cannot assure you that we will be able to maintain our qualification to conduct mobile network resale business under the enacted version of the notice. If we are not able to continue our mobile network resale business, our business, financial condition and results of operations may be adversely affected.

MIIT initiated another periodical pilot scheme for broadband access business by issuing the Notice on Liberalizing the Broadband Access Market to Private Capital on December 25, 2014, or the Broadband Notice, pursuant to which, the qualified private sector enterprises are encouraged, but not required, to apply to participate in the pilot scheme in broadband access business and the pilot scheme lasts for 3 years endingcommencing on December 31, 2017.March 1, 2015. From 2015 to 2017, MIIT issued a series of notices in succession to expand the pilot scheme to all cities in nine provinces and several designated cities in other provinces. Following expiration of the Broadband Notice, MIIT has not issued any public notice to extend the effective period of the pilot scheme or announced a long-term regulation, but the broadband business under the pilot scheme is permitted to continue in practice. As of the date of this annual report, we have applied for and qualified to provide broadband access services in 1920 cities such as Beijing, Shanghai, GuangzhouNanjing, Shenyang and Shenzhen.Xiamen.

We believe such pilot schemes represent the current administration’s continuous efforts in carrying out the recent policies of the PRC State Council and MIIT regarding encouraging private sectors to further participate in the telecommunication industry. The Broadband Notice specifically mentioned that the broadband access business is a basic telecommunication business. The Pilot Work Notice also specifically mentioned that the mobile network resale business which we believe shares something in common with our managed network services, is a second-category basic telecommunication business rather than a value-added telecommunication business. These pilot schemes, to some extent, reflect a legislative trend to welcome private enterprises (in comparison to the state-owned enterprise) to participate in basic telecommunication businesses in

the soon future. Nevertheless, although we believe these pilot schemes are not a practical change or modification to the current legal framework which our managed network service business might be subject to and only represent a legislative trend to open up the basic telecommunication business market to the private enterprises, new laws, regulations or government interpretations may also be promulgated from time to time to regulate the hosting service and managed network service or any of our related technology or services, which may require us to obtain additional, or expand existing, operating licenses or permits. Any of these factors could result in our disqualification from carrying out our current business, causing significant disruption to our business operations which may materially and adversely affect our business, financial condition and results of operations. We will be closely monitoring the developments of relevant laws and regulations.

In February 2018, MIIT issued an internal notice, or the MIIT Internal Notice, pursuant to which telecommunication authorities will carry out a special enforcement campaign to inspect the operations of certain licensed telecommunications operators according to applicable regulations and rules, including without limitation, the Circular on Clearing Up and Regulatory the Internet Access Service Market issued by the MIIT in January 2017. In particular, the authorities will pay special attention to any improper operational activities, such as unauthorized establishment of transmission network, unlicensed operation of cross-border business and improper sublease of broadband resources. According to MIIT Internal Notice, basic telecommunication service providers should exercise extra prudence when considering providing additional network resources to the enterprises under inspection. If the enterprise is found to be engaged innon-compliant operations, it may be subject to various penalties, including suspension of network access, suspension of approving its application for new operation permit until rectification being completed, being publicized as an operator with discredit record ornon-compliance record, enhanced oversight of the authority and limitation on new telecommunication business, depending on the seriousness of the violations and the rectification result. The MIIT Internal Notice mandates that the foregoing inspection and scrutiny to be completed by September 30, 2018. According to the MIIT Internal Notice, 47 industry players are subject to the special inspection, including two of our consolidated affiliated entities, 21Vianet Beijing and SZ DYX. As of the date of this annual report, we have not received any investigation notice or rectification order from the government authorities. We are closely communicating with thein-charge authority to clarify the inspection requirements of the authority and cooperate with them to review our business practices and compliance status. As part of our continuous efforts, in March 2018, we have joined and become a founding member of the China Cross-Border Data Telecommunications Industry Alliance, which is initiated by China Academy of Information and Communications Technology, an affiliate unit of the MIIT, aiming to strengthen industry self-discipline under the supervision of the regulator. Nevertheless, we cannot assure you that the government authorities will determine that we have been in full compliance with the regulatory requirements, especially the authority’s enhanced regulation on cross-border VPN business. If we are found to violate any operation requirements, we may be imposed on any of the administrative penalties mentioned in the MIIT Internal Notice, which may result in a material and adverse effect on our ability to conduct our operations and our financial conditions.

Under the New PRC Enterprise Income Tax Law, we may be classified as a “resident enterprise” of China. Such classification could result in unfavorable tax consequences to us and ournon-PRC holders of shares and ADSs.

Pursuant to the New PRC Enterprise Income Tax Law, or Newthe EIT Law, as recently amended on February 24, 2017, and its implementation rules, which became effective on January 1, 2008, an enterprise established outside of China with “de facto management bodies” within China is considered a “resident enterprise,” meaning that it can be treated in a manner similar to a Chinese enterprise for enterprise income tax, or EIT, purposes. Under the implementation rules of Newthe EIT Law, the term “de facto management body” is defined as the management body that exercises full and substantial control and overall management over the business, productions, personnel, accounts and properties of an enterprise. On April 22, 2009, the State Administration of Taxation issued the Notice Regarding the Determination of Chinese-Controlled Offshore Incorporated Enterprises as PRC Tax Resident Enterprises on the Basis of De Facto Management Bodies, or Circular 82, which is amended and supplemented by the Announcement Regarding the Determination of PRC Tax Resident Enterprises on the Basis of De Facto Management Bodies issued by the State Administration of Taxation on January 29, 2014. Circular 82

and its amendments sets out certain specific criteria and process for determining whether the “de facto management body” of a Chinese-controlled offshore incorporated enterprise is located in China. Given

We do not believe that we are a “resident enterprise” for PRC EIT purposes. However, the New EIT Law and its implementation rules are relatively new and ambiguous in termstax resident status of some definitions, requirements and detailed procedures, itan enterprise is unclear howsubject to determination by the PRC tax authorities will determine tax residency based onand uncertainties remain with respect to the factsinterpretation of each case.

the term “de facto management body”. If the PRC tax authorities determine that we are a “resident enterprise” for PRC EIT purposes, a number of unfavorable PRC tax consequences could follow: (i) we may be subject to EIT at a rate of 25% on our worldwide taxable income as well as PRC EIT reporting obligations; (ii) a 10% (or a lower rate under an applicable tax treaty, if any) withholding tax may be imposed on dividends we pay tonon-PRC enterprise holders (20% fornon-PRC individual holders) of our shares and ADSs; and (iii) a 10% PRC tax may apply to gains realized bynon-PRC enterprise holders (20% fornon-PRC individual holders) of our shares and ADSs from transferring our shares or ADSs, if such income is consideredPRC-source income.

Similarly, such unfavorable tax consequences could apply to our Hong Kong subsidiaries, if either of them is deemed to be a “resident enterprise” by the PRC tax authorities. Notwithstanding the foregoing provisions, the New EIT Law also provides that the dividends paid between “qualified resident enterprises” are exempt from EIT. If our Hong Kong subsidiaries are deemed “resident enterprises” for PRC EIT purposes, the dividends they receive from their PRC subsidiaries, including 21Vianet China, may constitute dividends between “qualified resident enterprises” and therefore qualify for tax exemption. However, the definition of “qualified resident enterprise” is unclear and the relevant PRC government authorities have not yet issued guidance with respect to the processing of outbound remittances to entities that are treated as resident enterprises for PRC EIT purposes. Even if such dividends qualify as “tax-exempt“tax-exempt income,” we cannot guarantee that such dividends will not be subject to any withholding tax.

We and our non-residentnon-tax resident investors face uncertainty with respect to indirect transfers of equity interests in PRC resident enterprises by theirnon-PRC holding companies.

Pursuant to the Notice on Strengthening Administration of Enterprise Income Tax for Share Transfers by Non-PRC Resident Enterprises, or Circular 698, issued by the State Administration of Taxation, which became effective retroactively as of January 1, 2008, where a non-resident enterprise investor transfers equity interests in a PRC resident enterprise indirectly by way of disposing of equity interests in an overseas holding company, the non-resident enterprise investor, being the transferor, may be subject to PRC enterprise income tax, if the indirect transfer is considered to be an abusive use of company structure without reasonable commercial purposes. As a result, gains derived from such indirect transfer may be subject to PRC withholding tax at the rate of up to 10%. In addition, the PRC resident enterprise may be required to provide necessary assistance to support the enforcement of Circular 698.

On February 3, 2015, the State Administration of Tax issued the Notice on Certain Corporate Income Tax Matters on Indirect TransfersTransfer of Properties by Non-ResidentNon-Tax Resident Enterprises, or Circular 7.7, which partially replaced and supplemented previous rules under the Notice on Strengthening Administration of Enterprise Income Tax for Share Transfers byNon-PRC Resident Enterprises, or Circular 7 has introduced a new tax regime that is significantly different from that under Circular 698.698, issued by the State Administration of Taxation on December 10, 2009. Circular 7 extends its tax jurisdiction to not only indirect transfers set forth under Circular 698 but also transactions involving transfer of other taxable assets, through the offshore transfer of a foreign intermediate holding company. In addition, Circular 7 provides clearer criteria than Circular 698 on how to assess reasonable commercial purposes and has introduced safe harbors for internal group restructurings and the purchase and sale of equity through a public securities market. Circular 7 also brings challenges to both the foreign transferor and transferee (or other person who is obligated to pay for the transfer) of the taxable assets. Where a non-residentnon-tax resident enterprise conducts an “indirect transfer” by transferring the taxable assets indirectly by disposing of the equity interests of an overseas holding company, the non-residentnon-tax resident enterprise being the transferor, or the transferee, or the PRC entity which directly owned the taxable assets may report to the relevant tax authority such indirect transfer. Using a “substance over form” principle, the PRC tax authority mayre-characterize such indirect transfer as a direct transfer of the equity interests in the PRC tax resident enterprise and other properties in China. As a result, gains derived from such indirect transfer may be subject to PRC enterprise income tax, and the transferee or other person who is obligated to pay for the transfer is obligated to withhold the applicable taxes, currently at a rate of up to 10% for the transfer of equity interests in a PRC resident enterprise. BothNevertheless, Circular 7 has introduced safe harbors for internal group restructurings and the purchase and sale of equity through a public securities market.

On October 17, 2017, the State Administration of Tax issued the Announcement of the State Administration of Taxation on Issues Concerning the Withholding ofNon-resident Enterprise Income Tax at Source, or SAT Bulletin 37, which came into effect on December 1, 2017 and concurrently abolished Circular 698. The SAT Bulletin 37 further clarifies the practice and procedure of the withholding ofnon-tax resident enterprise income tax. Pursuant to Circular 7 and SAT Bulletin 37, both the transferor and the transferee may be subject to penalties under PRC tax laws if the transferee fails to withhold the taxes and the transferor fails to pay the taxes.

However, as these rules and notices are relatively new and there is a lack of clear statutory interpretation, we face uncertainties on the reporting and consequences on future private equity financing transactions, share exchange or other transactions involving the transfer of shares in our company by investors that arenon-PRC resident enterprises, or sale or purchase of shares in othernon-PRC resident companies or other taxable assets by us. Our Cayman Islands holding company and othernon-PRC resident enterprises in our group may be subject to filing obligations or may be taxed if our Cayman Islands holding company and othernon-PRC resident enterprises in our group are transferors in such transactions, and may be subject to withholding obligations if our Cayman Islands holding company and othernon-PRC resident enterprises in our group are transferees in such

transactions. For the transfer of shares in our Cayman Islands holding company by investors that arenon-PRC resident enterprises, our PRC subsidiaries may be requested to assist in the filing under Circular 698 and Circular 7.7 and/or SAT Bulletin 37. As a result, we may be required to expend valuable resources to comply with these rules and notices or to request the relevant transferors from whom we purchase taxable assets to comply, or to establish that our Cayman Islands holding company and other non-residentnon-tax resident enterprises in our group should not be taxed under Circular 698 and Circular 7 and/or SAT Bulletin 37, which may have a material adverse effect on our financial condition and results of operations. There is no assurance that the tax authorities will not apply Circular 698 and Circular 7 and/or SAT Bulletin 37 to our offshore restructuring transactions wherenon-PRC resident investors were involved if any of such transactions were determined by the tax authorities to lack reasonable commercial purpose. As a result, we and ournon-PRC resident investors may be at risk of being taxed under Circular 698 and Circular 7 and/or SAT Bulletin 37 and may be required to comply with or to establish that we should not be taxed under Circular 698 and Circular 7 and/or SAT Bulletin 37, which may have a material adverse effect on our financial condition and results of operations or suchnon-PRC resident investors’ investments in us. We have conducted acquisition transactions in the past and may conduct additional acquisition transactions in the future. We cannot assure you that the PRC tax authorities will not, at their discretion, adjust any capital gains and impose tax return filing obligations on us or require us to provide assistance for the investigation of PRC tax authorities with respect thereto. Heightened scrutiny over acquisition transactions by the PRC tax authorities may have a negative impact on potential acquisitions we may pursue in the future.

Discontinuation of any of the preferential tax treatments available to us or imposition of any additional taxes could adversely affect our financial condition and results of operations.

The New EIT Law and its implementation rules, which became effective on January 1, 2008, unified the previously-existing separate income tax laws for domestic enterprises and FIEs and adopted a unified 25% EIT rate applicable to all resident enterprises in China, except for certain entities established prior to March 16, 2007 that are eligible for their existing preferential tax incentives, adjusted by certain transitionalphase-out rules promulgated by the State Council on December 26, 2007. In addition, certain enterprises may enjoy a preferential EIT rate of 15% under the New EIT Law if they qualify as High and New Technology Enterprise, or HNTE, subject to various qualification criteria.

A number of our PRC subsidiaries and consolidated affiliated entities, including 21Vianet Beijing, Gehua, BJ Fastweb, WiFire BJ (formerly known as BJ Tianwang)SH Blue Cloud, and GD Tianying,SZ DYX are entitled to enjoy a preferential tax rate of 15% due to their qualification as HNTE. The qualification as an HNTE is subject to annual administrative evaluation and a three-year review by the relevant authorities in China and a six-year reapplication.

In 2000 and 2012, Sichuan Aipu Network Co., Ltd., or SC Aipu, and Yunnan Aipu Network Technology Co., Ltd., or Yunnan Aipu, two companies within the Aipu Group, were qualified for a preferential tax rate of 15%. The preferential tax rate is awarded to companies that have operations in certain industries and meet the criteria of the Preferential Tax Policies for Development of the Western Regions. The qualification will need to be assessed on an annual basis.

In April 2011, 21Vianet (Xi’an) Information Outsourcing Industry Park Services Co., Ltd., or Xi’an Sub was qualified for a preferential tax rate of 15%. The preferential tax rate is awarded to companies that have operations in certain industries and meet the criteria of the Preferential Tax Policies for Development of the Western Regions. The qualification will need to be assessed on an annual basis.China.

In 2013, BJ iJoy was qualified as a software enterprise which allows it to utilize atwo-year 100% exemption for 2013 and 2014 followed by a three-year half-reduced EIT rate effective for the years from 2015 to 2017. The qualification will need to be assessed on an annual basis.

If 21Vianet Beijing, Gehua, BJ Fastweb, WiFire BJSH Blue Cloud and GD TianyingSZ DYX fail to maintain or renew their HNTE status, or if Xi’an Sub, SC Aipu and Yunnan Aipu are not able to enjoy their preferential tax treatment under Preferential Tax Policies for Development of the Western Regions, or if BJ iJoy fails to maintain or renew its software enterprise status, their applicable EIT rate may be increased to 25%, which could have a material adverse effect on our financial condition and results of operations.

The M&A Rules establish complex procedures for some acquisitions of Chinese companies by foreign investors, which could make it difficult for us to pursue growth through acquisitions in China.

The M&A Rules and other recently adopted regulations and rules concerning mergers and acquisitions established additional procedures and requirements that could make merger and acquisition activities by foreign

investors more time consuming and complex. In addition, the Implementing Rules Concerning Security Review on the Mergers and Acquisitions by Foreign Investors of Domestic Enterprises, issued by the MOC in August 2011, specify that mergers and acquisitions by foreign investors involved in “an industry related to national security” are subject to strict review by the MOC, and prohibit any activities attempting to bypass such security review, including by structuring the transaction through a proxy or contractual control arrangement. We believe that our business is not in an industry related to national security, but we cannot preclude the possibility that the MOC or other government agencies may publish explanations contrary to our understanding or broaden the scope of such security reviews in the future, in which case our future acquisitions in the PRC, including those by way of entering into contractual control arrangements with target entities, may be closely scrutinized or prohibited. Moreover, the Anti-Monopoly Law requires that the MOC be notified in advance of any concentration of undertaking if certain filing thresholds are triggered. Part of our growth strategy includes acquiring complementary businesses or assets in China. Complying with the requirements of the laws and regulations mentioned above and other PRC regulations to complete such transactions could be time-consuming, and any required approval processes, including obtaining approval from the MOC, may delay or inhibit our ability to complete such transactions, which could affect our ability to expand our business or maintain our market share. If any of our acquisitions were subject to the M&A Rule and were found not to be in compliance with the requirements of the M&A Rule in the future, relevant PRC regulatory agencies may impose fines and penalties on our operations in the PRC, limit our operating privileges in the PRC, or take other actions that could have a material adverse effect on our business, financial condition, results of operations, reputation and prospects.

PRC regulation of loans and direct investment by offshore holding companies to PRC entities may delay or prevent us from using the proceeds from our overseas offerings to make loans or additional capital contributions to our PRC subsidiaries or consolidated affiliated entities, which could materially and adversely affect our liquidity and our ability to fund and expand our business.

In utilizing the proceeds we received from our overseas offerings or in other financing activities, as an offshore holding company, we may make loans to our PRC subsidiaries or our consolidated affiliated entities in the PRC, or we may make additional capital contributions to our PRC subsidiaries or consolidated affiliated entities. Any loans to our PRC subsidiaries or our consolidated affiliated entities in the PRC are subject to PRC regulations. For example, loans by us to our PRC subsidiaries, which are FIEs, to finance their activities cannot exceed a statutory limitscap and must be registeredfiled with the State Administration of Foreign Exchange, or SAFE.SAFE, through the online filing system of SAFE after the loan agreement is signed and no later than three business days prior to the borrower withdraws any amount.

We may also decide to finance our PRC subsidiaries for operations in China by means of capital contributions. These capital contributions must be approved by or filed with the MOC or its local counterpart. We cannot assure you that we will be able to obtain these government approvals on a timely basis, if at all, with respect to future capital contributions by us to our subsidiaries. If we fail to receive such approvals, our ability to use the proceeds from our overseas offerings and to capitalize our PRC operations may be negatively affected, which could adversely affect our liquidity and our ability to fund and expand our business.

Governmental control of currency conversion may limit our ability to receive and utilize our revenues effectively.

We earn most of our revenues and incur most of our expenses in Renminbi; however, Renminbi is not freely convertible at present.

The PRC government continues to regulate conversion between Renminbi and foreign currencies, despite the significant reduction in its control in recent years over trade transactions involving import and export of goods and services as well as other frequent routine foreign exchange transactions. These transactions are known

as current account items. However, remittance of Renminbi by foreign investors into the PRC for the purposes of capital account items, such as capital contributions, is generally permitted upon obtaining specific approvals

from, or completing specific registrations or filings with, the relevant authorities on acase-by-case basis and is subject to a strict monitoring system. Regulations in the PRC on the remittance of Renminbi into the PRC for settlement of capital account items are developing gradually. Currently, our PRC subsidiaries may purchase foreign currencies for settlement of current account transactions, including payments of dividends to us, without the approval of the SAFE. However, foreign exchange transactions by our PRC subsidiaries under the capital account continue to be subject to significant foreign exchange controls and require the approval of or need to register or file with PRC governmental authorities, including the SAFE. In particular, if our PRC subsidiaries borrow foreign currency loans from us or other foreign lenders, these loans must first be registeredfiled with the SAFE. IfSAFE after the loan agreement is signed and at least three business days before the borrower draws any of our PRC subsidiaries, which are wholly foreign-owned enterprises, borrowsamount from the foreign currency,loan, and the accumulative amount of its foreign currency loans borrowed by a PRC subsidiary may not exceed the difference between the total investment and the registered capital of that PRC subsidiary.a statutory upper limit. If we finance our PRC subsidiaries by means of additional capital contributions, these capital contributions must be approved by certain government authorities, including the National Development and Reform Commission,or filed with the MOC or their respective local counterparts. Any existing and future restrictions on currency exchange may affect the ability of our PRC subsidiaries or affiliated entities to obtain foreign currencies, limit our ability to meet our foreign currency obligations or otherwise materially and adversely affect our business.

In March 2015, SAFE promulgated the Circular on Reforming the Administration Approach Regarding the Foreign Exchange Capital Settlement of Foreign-invested Enterprises, or SAFE Circular No. 19, which became effective on June 1, 2015. SAFE Circular No. 19 provides that, among other things, a foreign-invested enterprise may convert up to 100% of the foreign currency in its capital account into RMB on a discretionary basis according to the actual needs. On June 9, 2016, SAFE further issued the Circular of the State Administration of Foreign Exchange on Reforming and Regulating Policies on the Control over Foreign Exchange Settlement of Capital Accounts, or SAFE Circular No. 16, to further expand and strengthen such discretionary conversion reform under SAFE Circular No. 19. SAFE Circular No. 16 provides an integrated standard for conversion of foreign exchange under capital account items on a discretionary basis which applies to all enterprises registered in the PRC. Pursuant to SAFE Circular No. 16, in addition to foreign currency capital, the discretionary conversion policy expands to foreign currency debts borrowed by an enterprise (except financial institutions) and repatriated funds raised through overseas listing. In addition, SAFE Circular No. 16 has narrowed the scope of purposes for which an enterprise must not use the RMB funds so converted, which include, among others, (i) payment for expenditure beyond its business scope or otherwise as prohibited by the applicable laws and regulations; (ii) investment in securities or other financial products other than banks’ principal-secured products; (iii) provision of loans tonon-affiliated enterprises, except where it is expressly permitted in the business scope of the enterprise; and (iv) construction or purchase ofnon-self-used real properties, except for the real estate developer.

Fluctuation in exchange rates could have a material adverse effect on our results of operations and the value of your investment.

The conversion of Renminbi into foreign currencies, including U.S. dollars, is based on rates set by the People’s Bank of China. The PRC government allowed the Renminbi to appreciate by more than 20% against the U.S. dollar between July 2005 and July 2008. Between July 2008 and June 2010, this appreciation was halted and the exchange rate between the Renminbi and the U.S. dollar remained within a narrow band. As a consequence, the Renminbi fluctuated significantly during that period against other freely traded currencies, in tandem with the U.S. dollar. Since June 2010, the RMB has fluctuated against the U.S. dollar, at times significantly and unpredictably.unpredictably, and in recent years the RMB has depreciated significantly against the U.S. dollar. It is difficult to predict whether the depreciation will continue and how market forces or PRC or U.S. government policy may impact the exchange rate between the RMB and the U.S. dollar in the future.

As our costs and expenses are mostly denominated in RMB, the appreciation of the RMB against the U.S. dollar would increase our costs in U.S. dollar terms. In addition, as our operating subsidiaries and VIEs in China receive revenues in RMB, any significant depreciation of the RMB against the U.S. dollar may have a material and adverse effect on our revenues in U.S. dollar terms and financial condition, and the value of, and any

dividends payable on, our ordinary shares. For example, to the extent that we need to convert U.S. dollars into Renminbi for capital expenditures and working capital and other business purposes, appreciation of the Renminbi against the U.S. dollar would have an adverse effect on the Renminbi amount we would receive from the conversion. Conversely, if we decide to convert Renminbi into U.S. dollars for the purpose of making payments for dividends on our ordinary shares or ADSs, strategic acquisitions or investments or other business purposes, appreciation of the U.S. dollar against the Renminbi would have a negative effect on the U.S. dollar amount available to us. These and other effects on our financial data resulting from fluctuations in the value of the RMB against the U.S. dollar could have a material and adverse effect on the market price of our ADSs and your investment. See “Item 11. Quantitative and Qualitative Disclosures about Market Risk—Foreign Exchange Risk.”

PRC regulations relating to the establishment of offshore special purpose vehicles by PRC residents may subject our PRC resident beneficial owners to personal liability and limit our ability to acquire PRC companies, to inject capital into our PRC subsidiaries, limit our PRC subsidiaries’ ability to distribute profits to us, or otherwise materially and adversely affect us.

In October 2005, SAFE issued the Circular on the Relevant Issues in the Foreign Exchange Control over Financing and Return Investment Through Special Purpose Companies by Residents Inside China, or Circular

75, which is now replaced by the Circular on Relevant Issues Concerning Foreign Exchange Control on Domestic Residents’ Offshore Investment and Financing and Roundtrip Investment through Special Purpose Vehicles, or Circular 37, issued by SAFE on July 4, 2014. According to Circular 37, PRC residents are required to register with local SAFE branches in connection with their direct establishment or indirect control of an offshore entity for the purposes of overseas investment and financing, with such PRC residents’ legally owned assets or equity interests in domestic enterprises or offshore assets or interests, referred to in Circular 37 as a “special purpose vehicle.” The term “control” under Circular 37 is broadly defined as the operation rights, beneficiary rights or decision-making rights acquired by the PRC residents in the offshore special purpose vehicles or PRC companies by such means as acquisition, trust, proxy, voting rights, repurchase, convertible bonds or other arrangements. Circular 37 further requires amendment to the registration in the event of any changes with respect to the basic information of the special purpose vehicle, such as changes in a PRC resident individual shareholder, name or operation period; or any significant changes with respect to the special purpose vehicle, such as increase or decrease of capital contributed by PRC individuals, share transfer or exchange, merger, division or other material event. If the shareholders of the offshore holding company who are PRC residents do not complete their registration with the local SAFE branches, the PRC subsidiaries may be prohibited from distributing their profits and proceeds from any reduction in capital, share transfer or liquidation to the offshore company, and the offshore company may be restricted in its ability to contribute additional capital to its PRC subsidiaries. Moreover, failure to comply with SAFE registration and amendment requirements described above could result in liability under PRC law for evasion of applicable foreign exchange restrictions. On February 13, 2015, SAFE promulgated a Notice on Further Simplifying and Improving Foreign Exchange Administration Policy on Direct Investment, or SAFE Notice 13, which became effective on June 1, 2015. SAFE Notice 13 has delegated to the qualified banks the authority to register all PRC residents’ investment in “special purpose vehicle” pursuant to the Circular 37, except that those PRC residents who have failed to comply with Circular 37 will remain to fall into the jurisdiction of the local SAFE branches and must make their supplementary registration application with the local SAFE branches.

Our current PRC resident beneficial owners, including ourco-founders Sheng Chen and Jun Zhang, have filed the foreign exchange registration in connection with their respective overseas shareholding in our Company in accordance with the Circular 37 on June 10, 2014. We cannot assure you when ourco-founders can successfully complete their registrations. We have also requested other PRC residents who we know hold direct or indirect interest in our company to make the necessary applications, filings and amendments as required under Circular 37 and other related rules. We attempt to comply, and attempt to ensure that these PRC residents holding direct or indirect interest in our company comply, with the relevant requirements, and those persons holding direct or indirect interests in our securities whose identities and addresses we know and who are subject to

Circular 37 and the relevant SAFE regulations have conducted the registration procedures prescribed by Circular 37 and will update such registration. However, we may not be informed of the identities of all the PRC residents holding direct or indirect interest in our company, and we cannot provide any assurances that these PRC residents will comply with our request to make or obtain any applicable registrations or comply with other requirements required by Circular 37 or the relevant SAFE regulations. The failure or inability of PRC residents, including ourco-founders, to make any required registrations or comply with other requirements under Circular 37 and the relevant SAFE regulations may subject such PRC residents or our PRC subsidiaries to fines and legal sanctions and may also limit our ability to contribute additional capital into or provide loans to our PRC subsidiaries and our consolidated affiliated entities, limit our PRC subsidiaries’ ability to pay dividends or otherwise distribute profits to us, or otherwise materially and adversely affect us.

Failure to comply with the registration requirements for employee share option plans may subject our equity incentive plan participants who are PRC residents or us to fines and other legal or administrative sanctions.

Since 2007, SAFE has implemented rules requiring PRC residents who participate in employee stock option plans of overseas publicly listed companies to register with SAFE or its local office and complete certain other procedures. Effective on February 15, 2012, SAFE promulgated the Circular on the Relevant Issues Concerning Foreign Exchange Administration for Domestic Individuals Participating in an Employees Share Incentive Plan

of an Overseas-Listed Company, or SAFE Notice 7. Under SAFE Notice 7, PRC residents who participate in a share incentive plan of an overseas publicly listed company are required to register with SAFE and complete certain other procedures. PRC residents include directors, supervisors, management and employees of PRC domestic companies specified in the Administrative Regulations of the People’s Republic of China on Foreign Exchange, regardless of nationality. SAFE Notice 7 further requires that an agent should also be designated to handle matters in connection with the exercise or sale of share options granted under the share incentive plan to participants. We and the PRC residents to whom we have granted stock options are subject to SAFE Notice 7. If we or our PRC optionees fail to comply with these regulations, we or our PRC optionees may be subject to fines and other legal or administrative sanctions.

Risks Related to our ADSs

Potential uncertainty involving the going private transaction may adversely affect our business and the market price of our ADSs.

On June 10, 2015, our board of directors received a preliminary non-binding proposal letter from Mr. Sheng Chen, our chairman of the board of directors and chief executive officer, Kingsoft Corporation Limited and Tsinghua Unigroup International Co., Ltd. (together with Mr. Sheng Chen and Kingsoft Corporation Limited, the “Buyer Group”), to acquire all of our outstanding ordinary shares not already owned by the Buyer Group for US$23.00 in cash per ADS. On June 16, 2015, our board of directors formed a special committee of independent directors, or the Special Committee, to review and evaluate the proposal.

The going-private transaction, whether or not consummated, presents a risk of diverting management focus, employee attention and resources from other strategic opportunities and from operational matters. The development of the transaction, such as the entry into or the termination of any definitive agreement, may increase volatility of the trading price of our ADSs.

The market price of our ADSs has fluctuated and may continue to be volatile.

The trading prices of our ADSs are likely to be volatile and could fluctuate widely due to factors beyond our control. This may happen because of broad market and industry factors, such as the performance and fluctuation in the market prices or the underperformance or declining financial results of other companies based in China that have listed their securities in the United States in recent years. The securities of some of these companies have experienced significant volatility since their initial public offerings, including, in some cases, substantial price declines in the trading prices of their securities. The trading performances of other Chinese companies’ securities after their offerings may affect the attitudes of investors toward Chinese companies listed in the United States, which consequently may impact the trading performance of our ADSs, regardless of our actual operating performance. The recent ongoing administrative proceedings brought by SEC against five accounting firms in China, alleging that they refused to hand over documents to the SEC for ongoing investigations into certain China-based companies, occurs at a time when accounting scandals have eroded investor appetite for China-based companies. Any other negative news or perceptions about inadequate corporate governance practices or fraudulent accounting, corporate structure or matters of the Chinese companies may also negatively affect the attitudes of investors towards Chinese companies in general, including us, regardless of whether we have conducted any inappropriate activities. In addition, securities markets may from time to time experience significant price and volume fluctuations that are not related to our operating performance, which may have a material and adverse effect on the market price of our ADSs.

In addition, the market price for our ADSs has fluctuated since we first listed our ADSs on the NASDAQ Global Select Market on April 21, 2011, until April 11, 2016,2018, the trading prices of our ADSs have ranged from

US$8.314.17 to US$32.34 per ADS, and the last reported closing price on April 11, 20162018 was US$20.796.63 per ADS. The market price for our ADSs may be highly volatile and subject to wide fluctuations in response to factors including the following:

Our dual-class voting structure will limit your ability to influence corporate matters and could discourage others from pursuing any change of control transactions that holders of our Class A ordinary shares and ADSs may view as beneficial.

We have a dual-class voting structure such that our ordinary shares consist of Class A ordinary shares and Class B ordinary shares. In respect of matters requiring the votes of shareholders, holders of Class A ordinary shares are entitled to one vote per share, while holders of Class B ordinary shares are entitled to ten votes per share. Each Class B ordinary share is convertible into one Class A ordinary share at any time by the holder thereof, while Class A ordinary shares are not convertible into Class B ordinary shares or preferred shares under any circumstances. Upon any transfer of Class B ordinary shares by a holder thereof to any person or entity which is not an affiliate of such holder, such Class B ordinary shares shall be automatically and immediately converted into the equal number of Class A ordinary shares. Due to the disparate voting powers attached to these two classes, holders of our Class B ordinary shares have significant voting power over matters requiring shareholder approval. This concentrated control will limit your ability to influence corporate matters and could discourage others from pursuing any potential merger, takeover or other change of control transactions that holders of Class A ordinary shares and ADSs may view as beneficial.

Future sales of a substantial number of our ADSs in the public market, or the perception that these sales could occur, could cause the price of our ADSs to decline.

In the future, we may sell additional ADSs to raise capital, and our existing shareholders could sell substantial amounts of ADSs, including those issued upon the exercise of outstanding options, in the public market. We cannot predict the size of any future issuance of ADSs or the effect that future sales of our ADSs

would have on the market price of our ADSs. Any future sales of a substantial number of our ADSs in the public market, or the perception that these sales could occur, could cause the trading price of our ADSs to decline and impair our ability to raise capital through the sale of additional equity securities.

You may not have the same voting rights as the holders of our ordinary shares and may not receive voting materials in time to be able to exercise your right to vote.

Except as described in this annual report and in the deposit agreement, holders of our ADSs are not able to exercise voting rights attaching to the Class A ordinary shares evidenced by our ADSs on an individual basis.

Holders of our ADSs will appoint the depositary or its nominee as their representative to exercise the voting rights attaching to the Class A ordinary shares represented by the ADSs. Otherwise, you will not be able to exercise your right to vote unless you withdraw the Class A ordinary shares represented by the ADSs. However, you may not know of the meeting sufficiently in advance to withdraw the ordinary shares. If we ask for instructions from ADS holders, the depositary will notify you of the upcoming vote and arrange to deliver our voting materials to you. We cannot assure you that you will receive voting materials in time to instruct the depositary to vote, and it is possible that you, including persons who hold their ADSs through brokers, dealers or other third parties, will not have the opportunity to exercise a right to vote. The deposit agreement provides that if the depositary does not timely receive valid voting instructions from the ADS holders, then the depositary will, with certain limited exceptions, give a discretionary proxy to a person designated by us to vote such shares.

We are exempt from certain corporate governance requirements of NASDAQ and we intend to rely on certain exemptions.

Certain corporate governance practices in the Cayman Islands, which is our home country, are considerably different than the standards applied to U.S. domestic issuers. NASDAQ Marketplace Rules provide that foreign private issuers are exempt from certain corporate governance requirements of NASDAQ and may follow their home country practices, subject to certain exceptions and requirements to the extent that such exemptions would be contrary to U.S. federal securities laws and regulations. We currently follow our home country practice that: (i) does not require us to solicit proxy and hold meetings of our shareholders every year, (ii) does not restrict a company’s transactions with directors, requiring only that directors exercise a duty of care and owe certain fiduciary duties to the companies for which they serve, (iii) does not require us to obtain shareholder approval for issuing additional securities exceeding 20% of our outstanding ordinary shares, and (iv) does not require us to seek shareholders’ approval for amending our share incentive plan. As a result, our investors may not be provided with the benefits of certain corporate governance requirements of NASDAQ.

We may be classified as a passive foreign investment company for United States federal income tax purposes, which could result in adverse U.S. federal income tax consequences to U.S. holders of our ADSs or Class A ordinary shares.

Based on the market price of our ADSs and Class A ordinary shares, the value of our assets, and the composition of our assets and income, we believe that we were not a passive foreign investment company (a “PFIC”) for United States federal income tax purposes for our taxable year ended December 31, 20152017 and we do not expect to be a PFIC for the current year or for the foreseeable future. Nevertheless, the application of the PFIC rules is subject to ambiguity in several respects and, in addition, we must make a separate determination each year as to whether we are a PFIC (after the close of each taxable year). Accordingly, we cannot assure you that we will not be a PFIC for our current taxable year or for any future taxable year.

Anon-U.S. corporation, such as our company, will be considered a PFIC for United States federal income tax purposes for any taxable year if either (i) 75% or more of its gross income for such year consists of certain types of “passive” income or (ii) 50% or more of the value of its assets (determined on the basis of a quarterly average) during such year produce or are held for the production of passive income or the asset test.(the “asset test”). While we

do not anticipate being a PFIC, changes in the nature of our income or assets or the value of our assets may cause us to become a PFIC for the current or any subsequent taxable year. Under circumstances where revenues from activities that produce passive income significantly increase relative to our revenues from activities that producenon-passive income or where we determine not to deploy significant amounts of cash for active purposes, our risk of becoming classified as a PFIC may substantially increase.

Although the law in this regard is not entirely clear, we treat our variable interest entities as being owned by us for United States federal income tax purposes because we control their management decisions and we are entitled to substantially all of their economic benefits and, as a result, we consolidate their results of operations in our consolidated U.S. GAAP financial statements. If it were determined, however, that we are not the owner of our variable interest entities for United States federal income tax purposes, we would likely be treated as a PFIC for our taxable year ended December 31, 20152017 and for subsequent taxable years.

If we were to be or become a PFIC, a U.S. Holder (as defined in “Item 10.E. Additional Information—Taxation—United States Federal Income Tax Considerations—General”) may incur significantly increased United States income tax on gain recognized on the sale or other disposition of the ADSs or Class A ordinary shares and on the receipt of distributions on the ADSs or Class A ordinary shares to the extent such gain or distribution is treated as an “excess distribution” under the United States federal income tax rules. For more information, see “Item 10.E. Additional Information—Taxation—United States Federal Income Tax Considerations—Passive Foreign Investment Company Considerations.”

You may not be able to participate in rights offerings, may experience dilution of your holdings and you may not receive certain distributions on Class A ordinary shares if it is impractical to make them available to you.

We may from time to time distribute rights to our shareholders, including rights to acquire our securities. Under the deposit agreement for the ADSs, the depositary will not offer those rights to ADS holders unless both the rights and the underlying securities to be distributed to ADS holders are either registered under the Securities Act or exempt from registration under the Securities Act with respect to all holders of ADSs. We are under no obligation to file a registration statement with respect to any such rights or underlying securities or to endeavor to cause such a registration statement to be declared effective. In addition, we may not be able to take advantage of any exemptions from registration under the Securities Act. Accordingly, holders of our ADSs may be unable to participate in our rights offerings and may experience dilution in their holdings as a result.

In addition, the depositary of our ADSs has agreed to pay to you the cash dividends or other distributions it or the custodian receives on our ordinary shares or other deposited securities after deducting its fees and expenses. You will receive these distributions in proportion to the number of Class A ordinary shares your ADSs represent. However, the depositary may, at its discretion, decide that it is unlawful or impractical to make a distribution available to any holders of ADSs. For example, the depositary may determine that it is not practicable to distribute certain property through the mail, or that the value of certain distributions may be less than the cost of mailing them. In these cases, the depositary may decide not to distribute such property and you will not receive such distribution.

You may be subject to limitations on transfer of your ADSs.

Your ADSs represented by the ADRs are transferable on the books of the depositary. However, the depositary may close its transfer books at any time or from time to time when it deems expedient in connection with the performance of its duties. In addition, the depositary may refuse to deliver, transfer or register transfers of ADSs generally when our books or the books of the depositary are closed, or at any time if we or the depositary deem it advisable to do so because of any requirement of law or of any government or governmental body, or under any provision of the deposit agreement, or for any other reason.

You may face difficulties in protecting your interests, and your ability to protect your rights through the U.S. federal courts may be limited, because we are incorporated under Cayman Islands law, conduct all of our operations in China and a majority of our officers and directors reside outside the United States.

We are incorporated in the Cayman Islands and substantially all of our assets are located outside of the United States. We conduct all of our operations in China through our wholly-owned subsidiaries in China. The majority of our officers and directors reside outside the United States and a substantial portion of the assets of

those persons are located outside of the United States. As a result, it may be difficult for you to bring an action against us or against these individuals in the Cayman Islands or in China in the event that you believe that your rights have been infringed under theU.S. securities laws or otherwise. Even if you are successful in bringing an action of this kind, the laws of the Cayman Islands and of China may render you unable to enforce a judgment against our assets or the assets of our directors and officers. In addition, there is uncertainty as to whether the courts of the Cayman Islands or the PRC would recognize or enforce judgments of U.S. courts against us or our directors and officers predicated upon the civil liability provisions of the securities laws of the United States or any state, and it is uncertain whether such Cayman Islands or PRC courts would be competent to hear original actions brought in the Cayman Islands or the PRC against us or our directors and officers predicated upon the securities laws of the United States or any state, on the ground that such provisions are penal in nature.

Our corporate affairs are governed by our memorandum and articles of association and by the Companies Law (as amended)(2018 Revision) of the Cayman Islands and common law of the Cayman Islands. The rights of shareholders to take legal action against our directors and us, actions by minority shareholders and the fiduciary duties of our directors to us under Cayman Islands law are to a large extent governed by the common law of the Cayman Islands. The common law of the Cayman Islands is derived in part from comparatively limited judicial precedent in the Cayman Islands as well as from English common law, which has persuasive, but not binding, authority on a court in the Cayman Islands. The rights of our shareholders and the fiduciary duties of our directors under Cayman Islands law are not as clearly established as they would be under statutes or judicial precedents in the United States. In particular, the Cayman Islands has a less developed body of securities laws as compared to the United States, and provides significantly less protection to investors. In addition, Cayman Islands companies may not have standing to initiate a shareholder derivative action before the federal courts of the United States.

As a result of all of the above, our public shareholders may have more difficulty in protecting their interests through actions against our management, directors or major shareholders than they would as shareholders of a public company of the United States.

Our memorandum and articles of association contain anti-takeover provisions that could adversely affect the rights of holders of our ordinary shares and ADSs.

Our memorandum and articles of association contain certain provisions that could limit the ability of others to acquire control of our company, including our dual-class voting structure, and a provision that grants authority to our board of directors to establish from time to time one or more series of preferred shares without action by our shareholders and to determine, with respect to any series of preferred shares, the terms and rights of that series. These provisions could have the effect of depriving our shareholders of the opportunity to sell their shares at a premium over the prevailing market price by discouraging third parties from seeking to obtain control of our company in a tender offer or similar transactions.

We have incurred increased costs as a result of being a public company.

As a public company, we have incurred significant accounting, legal and other expenses that we did not incur as a private company. The Sarbanes-Oxley Act, as well as new rules subsequently implemented by the SEC and the NASDAQ Global Select Market, have detailed requirements concerning corporate governance practices of public companies including Section 404 of the Sarbanes-Oxley Act relating to internal controls over financial reporting. These new rules and regulations have increased our director and officer liability insurance, accounting,

legal and financial reporting compliance costs and have made certain corporate activities more time-consuming and costly. Therefore, we have incurred additional costs associated with our public company reporting requirements, and we cannot predict or estimate the amount of additional costs we may further incur or the timing of such costs.

If securities or industry analysts do not actively follow our business, or if they publish unfavorable research about our business, our ADS price and trading volume could decline.

The trading market for our ADS depends in part on the research and reports that securities or industry analysts publish about us or our business. If one or more of the analysts who covers us downgrades our ADSs or publishes unfavorable research about our business, our ADS price would likely decline. If one or more of these analysts ceases coverage of our company or fails to publish reports on us regularly, demand for our ADSs could decrease, which could cause our ADS price and trading volume to decline.

We commenced our operations in 1999, and through a series of corporate restructurings, set up a holding company, AsiaCloud Inc., or AsiaCloud, in October 2009 under the laws of the Cayman Islands. AsiaCloud was formerly a wholly-owned subsidiary of aBitCool Inc., or aBitCool, a company incorporated under the laws of the Cayman Islands. In October 2010, AsiaCloud effected a restructuring whereby AsiaCloud repurchased all its outstanding shares held by aBitCool and issued ordinary shares and preferred shares to the same shareholders of aBitCool. In connection with the restructuring, AsiaCloud subsequently changed its name to 21Vianet Group, Inc.

Due to certain restrictions under the PRC laws on foreign ownership of entities engaged in data center and telecommunications value-added services, we conduct our operations in China through contractual arrangements among us, our wholly-owned PRC subsidiaries, our variable interest entities and their shareholders. As a result of these contractual arrangements, we control our variable interest entities and have consolidated the financial information of our consolidated affiliated entities in our consolidated financial statements in accordance with U.S. GAAP. We own:control: (i) 100% of the equity interests in 21Vianet ChinaTechnology through our subsidiary, 21ViaNet Group Limited, or 21Vianet HK,China, which was incorporated in Hong Kong in May 2007;October 2002; (ii) 100% of the equity interests of SZ ZhuoaiyiBJ iJoy following completion of our acquisition of 100% equity interests in iJoy in April 2013; and (iii) 100% of the equity interests of WiFire Network through our subsidiary, aBitCool DG, which was incorporated in June 2014.

On April 21, 2011, our ADSs began trading on the NASDAQ Global Select Market under the ticker symbol “VNET.” We issued and sold a total of 14,950,000 ADSs, representing 89,700,000 Class A ordinary shares, at an initial offering price of US$15.00 per ADS.

As part of our growth strategy,From time to time, we have acquired companies that are complementary to our business, as well as made alternative investments and entered into strategic partnerships or alliances as we see fit.fit, we have also divested part of our business as part of our efforts to adjust our business development strategy. For example:

related services in Dongguan as well as create a research and development team that will focus on developing and implementing next generation networking technologies. As of the date of this annual report, Asia Cloud Investment and its subsidiary, Dongguan Asia Cloud Network Technology Co., Ltd., have not commenced any significant operations except for investments in certain floating rate principal unguaranteed securities with an aggregate amount of RMB102.3 million.

On June 10, 2015, our board of directors received a preliminarynon-binding proposal letter offer from Mr. Sheng Chen, Kingsoft Corporation Limited and Tsinghua Unigroup International Co., Ltd. (together with Mr. Sheng Chen and Kingsoft Corporation Limited, the Buyer Group“Buyer Group”) to acquire all of our outstanding ordinary shares not already owned by the Buyer Group for US$23.00 in cash per ADS. On June 16, 2015, our board of directors formed the Special Committee to review and evaluate the proposal. On June 30, 2016, our board of directors received a letter from the Buyer Group, stating that the Buyer Group would withdraw thenon-binding going private proposal with immediate effect.

In May 2016, we issued 31,996,874 Class A and 111,053,390 Class B ordinary shares toTus-Holdings Co., Ltd., orTus-Holdings, for an aggregate cash consideration of US$388 million. Upon the completion of this transaction,Tus-Holdings, through its affiliated investment vehicle, hold approximately 21.4% of our then total share capital, representing approximately 51.0% of the total voting power of us.

Our principal executive offices are located at M5, 1 Jiuxianqiao East Road, Chaoyang District, Beijing, 100016, the People’s Republic of China. Our telephone number at this address is +86 (10) 8456-2121. Our registered office in the Cayman Islands is located at the offices of Maples Corporate Services Limited, PO Box 309, Ugland House, Grand Cayman,KY1-1104, Cayman Islands. Our agent for service of process in the U.S. is Law Debenture Corporate Services Inc., located at 400 Madison Avenue, 4th Floor, New York, New York 10017.

See Item 4.C, “Organizational Structure” for a diagram illustrating our corporate structure as of the dated of this annual report.

Overview

We are a leading carrier-neutral internet data center services provider in China. We host our customers’ servers and networking equipment and provide interconnectivity to improve the performance, availability and

security of their internet infrastructure. We also provide managed network services to enable customers to deliver data across the internet in a faster and more reliable manner through our extensive data transmission network and our proprietary smart routing technology. Furthermore, we provide complementary value-added services, such as CDNcloud services, VPN services and last-mile wired broadband services to improve the security, speed and quality of data transmission in China.hybrid IT services. We started offering public cloud services in 2013, and private cloud and hybrid services in 2014.2014 and partnered with numerous cloud service providers to support our comprehensive cloud-neutral platform. We believe that the scale of our data center and networking assets as well as our carrier-neutrality position us well to capture opportunities and become a leader in the rapidly emerging market for cloud computing infrastructure services in China.

Our infrastructure consists of our high-quality data centers and an extensive data transmission network. We operate 1619 self-built data centers and 6938 partnered data centers located in over 3020 cities, including substantially all of China’s major internet hubs with 23,55629,080 cabinets under management that house 112,865163,187 servers as of December 31, 2015.2017. We adopt a distributed deployment method when choosing locations for our partnered data centers based on the specific requests of our customers, demands in different cities and our strategy for POP establishment; therefore, the locations and number of our partnered data centers are subject to change from to time. Our data transmission network includes 753476 POPs, which are access points from one place to the rest of the internet. Most of our data centers and all of our POPs are connected by our private optical fibers network across China.

As a carrier-neutral internet infrastructure services provider, our infrastructure is interconnected with the networks operated by all China’s telecommunications carriers, majornon-carriers and local internet service providers. The interconnectivity enables each of our data centers to function as a network access point for our customer’s data traffic. In addition, we believe that our proprietary smart routing technology allows us to automatically select an optimized route to direct our customers’ data traffic to ensure fast and reliable data transmission. We believe this advanced interconnectivity within and beyond our network distinguishes ourselves from our competitors and provides an effective solution to address our customers’ needs that arise from inadequate public internet infrastructure and network interconnectivity in China. As a result, businesses are increasingly relying upon internet infrastructure services providers and in particular, carrier-neutral internet infrastructure services providers, to enhance and optimize key elements of their IT and network infrastructure. Furthermore, we provide CDN services, VPN services, last-mile wired broadband services, public cloud services and private and hybrid cloud services and VPN services, which strengthens our capability to provide quality services and meet customer demand in our ecosystem.

We serve a diversified and loyal base of customers, depending on the different types of services provided by us, our customers include (i) enterprise customers for our hosting services, spanning many different industries and ranging from internet companies to government entities, from blue-chip enterprises to small- tomid-sized enterprises; (ii) individual household customers for last-mile wired broadband services; enterprises and (iii)(ii) enterprise and individual customers that signed for the Windows Azure and Office 365 services. Our average monthly churn rate as measured by monthly recurring revenues was approximately 1.7% in 2013. Our average monthly hosting churn rate, based on our core internet data center (IDC) business, was 0.6%0.2%, 0.7% and 0.2%0.5% in 20142015, 2016 and 2015, respectivley.2017, respectively. Our average monthly recurring revenue from our top 20 customers has increased from RMB57.1RMB74.8 million in 20142016 to RMB66.0RMB96.4 million (US$10.214.8 million) in 2015.2017.

We generate revenues from providing hosting and related services andused to provide managed network services. Our net revenues increased from RMB1,966.7 millionservices to enable customers to deliver data across the internet in 2013a faster and more reliable manner through our data transmission network. In 2017, we completed the disposal of the managed network services business segment, including CDN services, hosting area network services, route optimization business and last-mile broadband business, in order to RMB2,876.4 millionfocus more on expanding our core IDC business and capturing the growing demand in 2014 and to RMB3,634.4 million (US$561.1 million) in 2015, representing a CAGRthis market. Following completion of 35.9% from 2013 to 2015. The total number of cabinets under our management increased from 14,041 as of December 31, 2013 to 21,522 as of December 31, 2014 and to 23,556 as of December 31, 2015. Our average monthly recurring revenues increased from RMB146.6 million in 2013 to RMB208.4 million in 2014 and to RMB265.4 million (US41.0 million) in 2015. We recorded a net loss of RMB47.0 million, RMB328.5 million and RMB401.3 million (US$ 61.9 million) in

2013, 2014 and 2015, respectively, which reflected share-based compensation expenses of RMB67.8 million, RMB233.7 million and RMB190.0 million (US$29.3 million), respectively. Our results of operations also reflect the effectsdisposal, we have transferred all of our acquisitions duringequity interests in Aipu Group and continue to hold 33.3% equity interests in the respective periods.WiFire Entities.

Our Service Offerings

We primarily generate revenues from providing hosting and related services and managed network services. We provide hosting and related services to house servers and networking equipment in our data centers and connect them through our data transmission network, and offer other hosting related value-added services.network. We also provide cloud services, VPN services, hybrid IT services and other value-added services as part of our hosting and related services business, cloud services, CDN services and VPN services. Our managed network services allow our customers to transmit data across the internet in a faster and more reliable manner by leveraging our smart routing optimization technology through our hosting area network and data transmission network. Our managed network services also include last-mile wired broadband services.

Hosting and Related Servicesbusiness.

Our hosting and related services including the following:

Our data centers host the servers of our customers and meet their needs to deploy computing, network, storage and IT infrastructure. Our hosting and related services are scalable, allowing our customers to purchase space and power and upgrade connectivity and services as their requirements evolve. In addition, our customers benefit from our data centers’ wide range of physical security features, including sensitive smoke detection systems, fire suppression systems, secured access,around-the-clock video camera surveillance and security breach alarms. Our data centers are fully-redundant and feature resilient power supplies, energy efficient design, connection with multiple network providers and 24/7on-site support provided by our skilled engineers. As a result, we are able to guarantee 99.99% uptime for power in our service level agreements.

We believe another main reason customers choose our services is our access to multiple carriers and service providers and the availability of multiple-provider bandwidth. By securing multiple suppliers for connectivity and using redundant hardware, we are able to guarantee 99.9% internet connectivity uptime.

Managed Hosting Services (Colocation Services)

Our managed hosting services (colocation services) allow customers to lease partial or entire cabinetcabinets for their servers. Our customers have full control over their server(s) housed in our data centers. Depending on customer needs, we provide different levels of tailored server administration services, including operating system support and

assistance with updates, server monitoring, server backup and restoration, server security evaluation, firewall services, and disaster recovery. Our customers’ servers are housed in our data centers providing redundant power sources and heating, ventilating and air conditioning systems. Managed hosting service relieves customers from the daily pressures of IT infrastructure maintenance so that they can focus on their core businesses.

Customers have the option to either place their servers and equipment in standard cabinets dedicated for their private use, or in cabinets shared with other customers. They can customize their cabinet space for their servers, network connections and equipment. Customers can elect to buy the hardware that they place within their cabinets from their chosen suppliers. In addition, customers can also lease power-basedpower-enabled blank space, sometimes in a cage, where they can place their own cabinets in our data centers.centers or use our services to build their customized cabinet space.

Interconnectivity Services

Our interconnectivity services connect our customers with each other, connect our data centers with China’s internet backbones and other networks in the following ways:

Content Delivery Network Services

We also offer content delivery network services, or CDN services, primarily through Fastweb International Holdings, or Fastweb, a business we acquired in 2012 and through iJoy, which we acquired in 2013. Our CDN product portfolio provides customers with a cost-effective solution to their data connection needs in China, improving the reliability, scalability, security and speed of their internet services.

Cloud Services

We started providing public cloud services in 2013 and private and hybrid cloud services in 2014,

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Private and Hybrid Cloud Services. In December 2013, we entered into a definitive agreement with IBM to introduce IBM’s premier private cloud infrastructure service and bring high-value managed private and hybrid cloud services to China. Private and hybrid cloudIn October 2016, services are mostly provided to multi-national corporations or large enterprise customers to meet their specific needs for private and hybrid cloud services. Our private and hybrid cloud serviceof IBM Cloud (previously known as Bluemix) were made generally available in China through our partnershipthe collaboration with IBM is specifically designed for the customers based on their requirements to ensure that they can exert the most effective control of data, security and quality of service. The customers can either use our infrastructure orus. In particular, we can build(i) provide the infrastructure of IBM Cloud combined with the latest technologies of IBM (ii) are responsible for theend-to-end operation of IBM Cloud in their facilities, The customers can then upload their applications to the virtual servers for their private useChina; and we will(iii) provide related manageda comprehensive set of services, such as database managementIoT and Cloudant, to China’s burgeoning developer community. Our services firewall services, server load balancing services, data backupprovided a set of tools for China’s software developers to efficiently develop new apps and recovery services, server management services, BGP internet access and VPN services. Currently, we partner with IBM to provide cloud infrastructure services and managed services.technologies based on readily available models. We also provide information technology service management services to enterprise customers of Unisys based on our cooperation contract with Unisys.

VPN Services

We also offer virtual private network services, or VPN services, primarily through Dermot Holdings Limited and its subsidiaries, or Dermot Entities, which we acquired in August 2014. Dermot Entities offer customers a comprehensive portfolio of customized VPN solutions for both enterprise customers seeking multi-point connectivity and carrier customers seeking to provisionoff-net customer locations. With over 4050 POPs across China, Hong Kong, Singapore, Taiwan and Vietnam, Dermot Entities provide fully-managed network enabling connectivity to more than 700 cities in the region for many “blue-chip” customers across many verticals, including manufacturing, logistics, retail, financial services, eSports, real estate, food and financial services.beverage and technology.

Hybrid IT Services

Our hybrid IT services provide customers with a complete package of infrastructure service offerings, conveniently bundled to expedite the customer’s process to launch their applications and products to the extent possible. In conjunction with our infrastructure as a service (IAAS) platform, hybrid IT services combine colocation, servers, connectivity, storage and customer service to save IT infrastructure installation time, and provide a complete, reliable, and secured environment for customer’s IT demands. As more customers move their IT resources to the cloud, our cloud-neutral platform will enable our hybrid IT services to provide both private and public cloud services as well as their inter-linked connections.

Other Value-Added Services

To complement our hosting services and enhance our customers’ experiences, we also provide value-added services, including firewall services, server load balancing, data backup and recovery, data center management, server management, and backup server services.