This Annual Report on Form 10-K contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which statements involve substantial risks and uncertainties. Forward-looking statements generally relate to future events or our future financial or operating performance. In some cases, you can identify forward-looking statements because they contain words such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “could,” “intends,” “target,” “projects,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these words or other similar terms or expressions that concern our expectations, strategy, plans or intentions. Forward-looking statements contained in this Annual Report on Form 10-K include, but are not limited to, statements about:

We caution you that the foregoing list may not contain all of the forward-looking statements made in this Annual Report on Form 10-K.

The numbers of mDAU presented in this Annual Report on Form 10-K are based on internal company data. While these numbers are based on what we believe to be reasonable estimates for the applicable period of measurement, there are inherent challenges in measuring usage and engagement across our large number of total accounts around the world. Furthermore, our metrics may be impacted by our information quality efforts, which are our overall efforts to reduce malicious activity on the service, inclusive of spam, malicious automation, and fake accounts. For example, there are a number of false or spam accounts in existence on our platform. We have performed an internal review of a sample of accounts and estimate that the average of false or spam accounts during the fourth quarter of 20202021 represented fewer than 5% of our mDAU during the quarter. The false or spam accounts for a period represents the average of false or spam accounts in the samples during each monthly analysis period during the quarter. In making this determination, we applied significant judgment, so our estimation of false or spam accounts may not accurately represent the actual number of such accounts, and the actual number of false or spam accounts could be higher than we have estimated. We are continually seeking to improve our ability to estimate the total number of spam accounts and eliminate them from the calculation of our mDAU, and have made improvements in our spam detection capabilities that have resulted in the suspension of a large number of spam, malicious automation, and fake accounts. We intend to continue to make such improvements. After we determine an account is spam, malicious automation, or fake, we stop counting it in our mDAU, or other related metrics. We also treat multiple accounts held by a single person or organization as multiple mDAU because we permit people and organizations to have more than one account. Additionally, some accounts used by organizations are used by many people within the organization. As such, the calculations of our mDAU may not accurately reflect the actual number of people or organizations using our platform.

In addition, geographic location data collected for purposes of reporting the geographic location of our mDAU is based on the IP address or phone number associated with the account when an account is initially registered on Twitter. The IP address or phone number may not always accurately reflect a person’s actual location at the time they engaged with our platform. For example, someone accessing Twitter from the location of the proxy server that the person connects to rather than from the person’s actual location.

We regularly review and may adjust our processes for calculating our internal metrics to improve their accuracy.

Twitter is what’s happening in the world and what people are talking about right now.

Our primary product, Twitter, is a global platform for public self-expression and conversation in real time. Twitter allowsWe have democratized content creation and distribution so people tocan consume, create, distribute and discover content about the topics and has democratized content creation and distribution.events they care about most. Through Topics, Interests, and Trends, we help people discover what’s happening live. We also continue to implementthrough text, images, on demand and live broadcastsvideo, and on-demand videoaudio from people, content across Twitter, including through partnerships withpartners, media outletsorganizations, advertisers and our platform partners.others. Media outlets, websites, and our platformother partners also help extend the reach of Twitter content by distributing Tweets beyond our products to complement their content. People can also express themselves using creation tools like Voice Tweetsapp and Fleets, which allows everyone to start conversations in a new way – with their voice or with their fleeting thoughts using text, reactions to Tweets, photos or videos.website.

In 2020,2021, we continued our work to serve the public conversation by helping people find trusted sources of information and by better organizing and surfacing the many topics and interests that bring people to Twitter. Twitter, with a focus on personalization and selection. We launched products to continue helping people stay informed and discuss what matters to them such as Twitter Spaces, a new way to have live audio conversations on Twitter, and Communities, a new way to easily find and connect with people who have similar interests. We also worked to help people and businesses get paid on Twitter by introducing Ticketed Spaces, Super Follows, and Tips, which give people the ability to pay creators using a variety of payment methods to send currency or Bitcoin to creators. We also introduced Twitter Blue, Twitter’s first-ever consumer subscription offering. Twitter Blue allows our most passionate and engaged accounts to pay for exclusive features and perks that enhance and complement their existing Twitter experience.

We are making it easier to follow and participate in healthier conversations by rolling out new conversation settings globally, and giving people everywhere more control over the conversations they start on Twitter. In addition, we made significant progress on our brand and direct response roadmap with updated ad formats, stronger attribution, and improved targeting. We also continued to iterate on our revamped Mobile Application Promotion (MAP) offering. Wehave furthered our efforts to improve the health of the platform, as we work to make sure that people and advertisers feel safe being a part of the conversation and are able tocan find credible information on our service. Major areas of focus within health include reducing abuse, providing more context around misinformation, and protecting the integrity of civic-related conversations.

Our Promoted Products enable our advertisers to launch products and services and promote their brands, amplify their visibility and reach,products and connect with what’s happening to extend the conversation around their advertising campaigns.services. We enable our advertisers to target an audience based on a variety of factors, including who an account follows and actions taken on our platform, such as Tweets created and engagement with Tweets. We believe this data produces a clear and real-time signal of what is relevant to that person's interests,account, greatly enhancing the relevanceperformance of the ads we can display and enhancing our targeting capabilities forserve on behalf of advertisers. Our Promoted Products are incorporated into our platform as native advertising and are designed to be as compelling and useful to people on Twitter as organic content on our platform.

Currently, our Promoted Products consist of:

Advertisers can also run short video ads either before or around premium video content, such as duringbefore live premium video content from publishing partners or clips from a variety of interest categories such as news, sports and entertainment. Our technology dynamically inserts those advertisers' ads into the relevant videos and delivers the ads to the audience targeted by those advertisers. We may pay content partners a portion of our advertising revenue for the right to use and distribute their content on our platform. In addition, Amplify Sponsorships allow advertisers to build brand association by sponsoring premium video content from a single publishing partner, including livepartner.

We recently redesigned our Amplify pre-roll video video clips, and other storytelling formats like Sponsored Moments.

Our technology platform and information database enableenables us to provide targeting capabilities based on audience attributes like geography, interests, keyword, conversation, content, and events that make it possible for advertisers to promote their brands, products and services, amplify their visibility and reach, and complement and extend the conversation around their advertising campaigns.

Our platform also enables customers to advertise across the mobile ecosystem, both on Twitter's owned and operated properties as well as off Twitter on third-party publishers’ websites, applications and other offerings. We enable advertisers to extend their reach beyond Twitter through:

Video is an important way to stay informed, on Twitter, enabling people on Twitter and our premium content ownerspartners to better share experiences, engage in events, and converse with broader audiences. We continue to improve the conversation around global events and to increase reach, engagement, and engagementmonetization for content ownerspartners and advertisers around the world through brand safe live-streaming, highlight video clips, and video-on-demand agreements designed to complement the content from people on Twitter and licensed live and on-demand video content already available on Twitter across a number of verticals including sports, news, gaming and entertainment. These partnerships enable content publishers and advertisers to reach fans where it all happens, when it’s happening.

The Twitter Developer Platform (formerly Developer and Enterprise Solutions (DES) is our software-as-a-service platform that enablesSolutions) empowers developers around the world to build products around the aggregated, anonymized wealth of datatools for people and businesses using our public application programming interface (API), or in simpler terms, it gives people more ways to interact with what’s happening on Twitter. Developers use Twitter application programming interfaces (APIs) to build applicationsThis includes data and insights from Tweets, Spaces, polls, and other products for themselves, consumers, and business customers. DESfeatures that help make Twitter more useful to more people in more places. The Twitter Developer Platform serves commercial and non-commercial developers including businesses, academics, and consumer developers, among others. We believe this work has the potential to help us with our efforts to improve the health of and participation in the public conversation. WebsitesDevelopers use Twitter’s platform to build apps and applications integratingwebsites that integrate with our publicly available APIs to improve people’s experience on Twitter by helpingconnecting them with the conversations they care about. They also help brands and publishers engage with what’s happening and gain insights from the public conversation.

We also offer paid enterprise access to our publicTwitter data streams for partners with commercial use cases and those who wish to access more data beyond what is available for free.free through our public APIs. Paying DES customersdevelopers typically sign multi-year subscriptions, or enterprise agreements, based on the type and volume of usage. Our enterprisecommercial data products and services offer more sophisticated data analysis toolsAPIs and other services to support developers in building mature businesses on our platform.developers. Our customer-centric approach positions both Twitter and our key partners for greater growth and monetization, and we are investing in deeper partnerships with select solution providers to help businesses and organizations realize greater value from our data and platform. TheA goal of our platform product is to make it easy for developers to integrate seamlessly with Twitter, while protecting the privacy and safety of the people who use Twitter.

Our business is characterized by rapid technological change, frequent product innovation and the continuously evolving preferences and expectations of people on Twitter, advertisers, content partners, platform partners and developers. We face significant competition in every aspect of our business, including from companies that provide tools to facilitate communications and the sharing of information, companies that enable marketers to display advertising, and other online ad networks, exchanges and platforms. We also compete to attract, engage, and retain people who use our products, and to attract and retain marketers, content and platform partners, and developers. We have seen escalating competition for digital ad spending and expect this trend to continue. We also compete to attract and retain employees, especially software engineers, designers, and product managers.

We compete with the following companies for people’s attention and for advertisers’ budgets:

As we introduce new products, as our existing products evolve, or as other companies introduce new products and services, we may become subject to additional competition.

Our industry is evolving rapidly and is highly competitive. See the sections titled “Risk Factors—If we are unable to compete effectively for people to use our platform, and for content and data partners, our business and operating results could be harmed.”, “Risk Factors—If we are unable to compete effectively for advertising spend, our business and operating results could be harmed.” and “Risk Factors—We depend on highly skilled personnel to grow and operate our business. If we are unable to hire, retain and motivate our personnel, we may not be able to grow effectively."

Twitter is composed of a set of core, scalable and distributed services that are built from proprietary and open source technologies. These systems are capable of delivering billions of messages, including images and video, to hundreds of millions of people a day in an efficient and reliable way. We continue to invest in our existing products and services as well as develop new products and services through research and product development. We also continue to invest in protecting the safety, security and integrity of our platform by investing in both people and technology, including machine learning.

We have a global sales force and sales support staff that is focused on attracting and retaining advertisers while certain advertisers use our self-serve advertising platform to launch and manage their advertising campaigns. Our sales force and sales support staff assist advertisers throughout the advertising campaign cycle, from pre-purchase decision making to real-time optimizations as they utilize our campaign management tools, and to post-campaign analytics reports to assess the effectiveness of their advertising campaigns.

We use marketing campaigns to help drive audiences to our platform. In 2020,2021, we continued to deliver marketing campaigns focused on celebrating and highlighting the voices of the people who make Twitter unique. We also continued to highlight our value proposition for advertisers, including how brands turn to Twitter to launch something new, and connect with what’s happening.

We seek to protect our intellectual property rights by relying on federal, state and common law rights in the United States and other countries, as well as contractual restrictions. We generally enter into confidentiality and invention assignment agreements with our employees and contractors, and confidentiality agreements with other third parties, in order to limit access to, and disclosure and use of, our confidential information and proprietary technology. In addition to these contractual arrangements, we also rely on a combination of trademarks, trade dress, domain names, copyrights, trade secrets and patents to help protect our brand and our other intellectual property.

We are subject to a number of U.S. federal and state and foreign laws and regulations that involve matters central to our business. These laws and regulations may involve privacy, data protection, security,cybersecurity, rights of publicity, content regulation, data localization, intellectual property, competition, protection of minors, consumer protection, credit card processing, taxation or other subjects. Many laws and regulations impacting our business are being proposed, are still evolving or are being tested in courts and could be interpreted and applied in a manner that is inconsistent from country to country and inconsistent with our current policies and practices and in ways that could harm our business. In addition, the application and interpretation of these laws and regulations often are uncertain, particularly in the new and rapidly evolving industry in which we operate.

With regard to privacy, data protection and security,cybersecurity, we are subject to a variety of federal, state and foreign laws and regulations. For example, the California Consumer Privacy Act (CCPA), which went into effect on January 1, 2020, requires covered companies to, among other things, provide new disclosures to California consumers, and afford such consumers new abilitiesthe ability to opt-out of certain sales of personal information. Similar legislation has been proposed or adopted in other states. Additionally, a new California ballot initiative, the California Privacy Rights Act (CPRA), was passed in November 2020. The CPRA creates created obligations relating to consumer data beginning on January 1, 2022, with implementing regulations expected on or before July 1, 2022, and enforcement beginning July 1, 2023. Aspects of the CCPA, the CPRA and these other state laws and regulations, as well as their interpretation and enforcement, remain unclear, and we may be required to modify our practices in an effort to comply with them. Foreign data protection, privacy, security,cybersecurity, consumer protection, content regulation and other laws and regulations are often more restrictive or burdensome than those in the United States. For example, the General Data Protection Regulation, or the GDPR, imposes stringent operational requirements for entities processing personal information and significant penalties for non-compliance. There are also a number of legislative proposals pending before the U.S. Congress, various state legislative bodies and foreign governments concerning content regulation and data protection that could affect us.

In March 2011, to resolve an investigation into various incidents, we entered into a settlement agreement with the Federal Trade Commission, or FTC, that, among other things, requires us to establish an information security program designed to protect non-public consumer information and also requires that we obtain biennial independent security assessments. The obligations under the settlement agreement remain in effect until the later of March 2, 2031, or the date 20 years after the date, if any, on which the U.S. government or the FTC files a complaint in federal court alleging any violation of the order. On July 28, 2020, we received a draft complaint from the FTC alleging violation of the order and the Federal Trade Commission Act (FTC Act). The allegations relate to our use of phone number and/or email address data provided for safety and security purposes for targeted advertising during periods between 2013 and 2019. The matter remains unresolved, and there can be no assurance as to the timing or the terms of any final outcome. Violation of other existing or future regulatory orders, settlements, or consent decrees could subject us to substantial monetary fines and other penalties that could negatively affect our financial condition and results of operations.

People may be restricted from accessing Twitter from certain countries, and other countries have intermittently restricted access to Twitter. For example, Twitter is not directly accessible in China and has been intermittently blocked in the past in Turkey and certain of our SMS messages have been blocked in Saudi Arabia.Turkey. It is possible that other governments may seek to restrict access to or block our website or mobile applications, censor content available through our products or impose other restrictions that may affect the accessibility or usability of Twitter for an extended period of time or indefinitely, including because of our decisions with respect to the enforcement of our rules. For instance, some countries have enacted laws that allow websites to be blocked for hosting certain types of content.

For additional information, see the section titled “Risk Factors—Our business is subject to complex and evolving U.S. and foreign laws and regulations. These laws and regulations are subject to change and uncertain interpretation, and could result in claims, changes to our business practices, monetary penalties, increased cost of operations or declines in mDAU growth, mDAU engagement or ad engagement, or otherwise harm our business.”

We believe the strength of our workforce is critical to our success as we strive to become a more inclusive, diverse, and diverseaccessible technology company. Our key human capital management objectives are to attract, retain, and develop the talent we need to deliver on our commitment to serve the public conversation in a safe and responsible way by offering exceptional products and services. Examples of our key programs and initiatives that are focused to achieve these objectives include:

We have made significant progress towards our inclusion, diversity, equity, and diversityaccessibility objectives through leadership, transparency and accountability. In 2021, we focused on equity across every stage of our employee lifecycle: recruitment and hiring, onboarding, compensation and pay transparency, learning and development, and our work cultivating an inclusive environment across teams and regional geographies with our Business Resource Groups at the center. As we continue to learn, we also evolved our vision to more impactfully integrate accessibility and equity into our work and merged the Inclusion and Diversity (I&D) and Accessibility teams into a new Inclusion, Diversity, Equity, & Accessibility team to reflect this commitment.

As of December 31, 2020,2021, we employed over 5,5007,500 full-time employees.

Our business operations are subject to numerous risks and uncertainties, including those outside of our control, that could cause our business, financial condition or operating results to be harmed, including risks regarding the following:

Our mDAU and their level of engagement with advertising are critical to our success and our long-term financial performance will continue to be significantly determined by our success in increasing the growth rate of our mDAU as well as the number of ad engagements. Our mDAU growth rate has fluctuated over time, and it may slow or decline.decline in general or in certain geographies or among certain groups. To the extent our mDAU growth rate slows or the absolute number of mDAU declines, our revenue growth will become dependent on our ability to increase levels of engagement on Twitter, generate advertiser demand, and increase revenue growth from third-party publishers’ websites and applications, data licensing and other offerings. We generate a substantial majority of our revenue based upon engagement with the ads that we display. A number of factors have affected and could potentially negatively affect mDAU growth and engagement, including if:

We have made certain projections regarding our mDAU growth. If we are unable to achieve these projections, or to generally increase our mDAU or engagement, or if these metrics decline, our products and services could be less attractive to people on Twitter, as well as to advertisers, content partners and platform partners, which would have a material and adverse impact on our business, financial condition and operating results.

The substantial majority of our revenue is currently generated from third parties advertising on Twitter. We generate substantially all of our advertising revenue through the sale of our Promoted Products: Promoted Tweets, Promoted AccountsAds, Twitter Amplify, Follower Ads and Promoted Trends.Twitter Takeover. As is common in our industry, our advertisers do not have long-term advertising commitments with us. As a result of the COVID-19 pandemic, we experienced a reduction in advertiser demand in the first half of 2020 compared to the same period in 2019. In the second half of 2020, revenue increased compared to the same period in 2019 as advertisers increased their investment on Twitter, engaging our larger audience around the return of events as well as increased and previously delayed product launches. However, we may experience reduced advertiser demand and decreased advertising revenue in future quarters due to the ongoing and potential future impacts of the COVID-19 pandemic.

In addition, many of our advertisers purchase our advertising services through one of several large advertising agencies' holding companies. To sustain or increase our revenue, we must add new advertisers and encourage existing advertisers to maintain or increase the amount of advertising inventory purchased through our platform and adopt new features and functionalities that we add to our platform. However, advertising agencies and potential new advertisers may view our Promoted Products or any new products or services we offer as experimental and unproven, and we may need to devote additional time and resources to educate them about our products and services. Further, our advertisers’ ability to effectively target their advertising to our audience’s interests may be impacted by the degree to which people on Twitter agree in our settings to certain types of personalization or ad targeting, which could have an impact on our revenue. People that already have accounts may change their choices as a result of changes to our privacy control settings that we have implemented or may implement in the future, and people new to Twitter may choose varied levels of personalization, whether in connection with future changes we make to product privacy settings, regulations, regulatory actions, the customer experience, or otherwise.

We face intense competition for people to use our platform, and for content and data partners. We compete for our audience against a variety of social networking platforms, messaging companies and media companies, some of which have greater financial resources, larger audiences or more established relationships with advertisers, such as Meta (including Facebook, (including Instagram and WhatsApp), Alphabet (including Google and YouTube), Microsoft (including LinkedIn), Snapchat, TikTok, Pinterest and Verizon Media Group,Yahoo, or in certain regions WeChat, Kakao and Line. New or existing competitors may draw people towards their products or services and away from ours by introducing new product features, including features similar to those we offer, investing their greater resources in audience acquisition efforts or otherwise developing products or services that audiences choose to engage with rather than Twitter, any of which could decrease mDAU growth or engagement and negatively affect our business.

We also compete with respect to content generated by our content partners and the availability of applications developed by platform partners. We may not establish and maintain relationships with content partners who publish on our platform or platform partners who develop applications that integrate with our platform. Our content and platform partners may choose to publish content on, or develop applications for, other platforms, and if they cease to utilize our platform or decrease their use of our platform, then mDAU, engagement, and advertising revenue may decline.

We believe that our ability to compete effectively for audiences and content partners depends upon many factors both within and beyond our control, including:

If we are not able to compete effectively for audience, content and platform partners, our mDAU and engagement would decline and our business and operating results would be materially and adversely impacted.

We face significant competition for advertiser spend. We compete against online and mobile businesses and traditional media outlets, such as television, radio and print, for advertising budgets. We also compete with advertising networks, exchanges, demand side platforms and other platforms, such as Google AdSense, DoubleClick Ad Exchange, Nexage and Brightroll Ad Exchanges, Verizon Media Group, and Microsoft Media Network, for marketing budgets and in the development of the tools and systems for managing and optimizing advertising campaigns. In order to grow our revenue and improve our operating results, we must increase our share of spending on advertising relative to our competitors, many of which are larger companies that offer more traditional and widely accepted advertising products. In addition, some of our larger competitors have substantially broader product or service offerings and leverage their relationships based on other products or services to gain additional share of advertising budgets.

We believe that our ability to compete effectively for advertiser spend depends upon many factors both within and beyond our control, including:

If we are not able to compete effectively for advertiser spend, our mDAU and engagement would decline and our business and operating results would be materially and adversely impacted.

We believe that our long-term success depends on our ability to improve the health of the public conversation on Twitter. We have made this one of our top priorities and have focused our efforts on improving the quality of that conversation, including by devoting substantial internal resources to our strategy. These efforts include the reduction of abuse, harassment, spam, manipulation and malicious automation on the platform, as well as a focus on improving information quality (including information around elections and the 2020 U.S. elections)COVID-19 pandemic), and the health of conversation on Twitter. Some of the health initiatives that we have implemented as part of our ongoing commitment to a healthy public conversation have negatively impacted, and may in the future negatively impact, our publicly reported metrics in a few ways.

First, our health efforts include the removal of accounts pursuant to our terms and services that are abusive, spammy, fake or malicious, and these accounts may have been included in our mDAU, as well as actions taken to detect and challenge potentially automated, spammy or malicious accounts during the sign-up process. If we make a sudden improvement to one of the algorithms we use to detect spammy or suspicious behavior, we may remove a larger number of accounts as a result and impact the year-over-year average of mDAU growth. Additionally, we may remove certain influential accounts for violations of our terms of service and the removal of such accounts has in the past reduced and may in the future reduce our mDAU growth and engagement.

Second, we are also making active decisions to prioritize certain health relatedhealth-related initiatives over other near-term product improvements that may drive more usage of Twitter as a daily utility. These decisions may not be consistent with the short-term expectations of our advertising customers or investors and may not produce the long-term benefits that we expect, in which case our mDAU growth and engagement, our relationships with advertisers and our business and operating results could be harmed.

Our decision to invest in the long-term health of our service may not produce the long-term benefits that we expect, in which case our mDAU growth and engagement, our relationships with advertisers and our business and operating results would be adversely impacted, and may not be consistent with the expectations of investors, which could have a negative effect on the trading price of our common stock.

We encourage employees to quickly develop and help us launch new and innovative features. We focus on improving the experience for people using our products and services, which includes measures to help protect the privacy of people on Twitter. Similarly, we prioritize developing new and improved products and services for advertisers on our platform. We frequently make product, product feature and service decisions that may reduce our short-term operating results if we believe that the decisions are consistent with our goals to improve the long-term experience for people on Twitter and/or performance for advertisers, which we believe will improve our operating results over the long term. For example, in January 2022, we completed the sale of our MoPub business. The sale of MoPub enables us to accelerate the development of our core revenue products and drive growth across key areas of the business, including performance-based advertising, small and medium-sized business (SMB) offerings, and commerce initiatives on Twitter. While the product, engineering, and go-to-market teams associated with MoPub began to shift over to these key focus areas immediately upon the closing of the transaction, it will take time for their work to deliver results. As a result, we do not expect to recoup the full revenue loss associated with the sale of MoPub in 2022, but there are no changes to our long-term goals with an increased focus and additional resources working on increasing our market share within the addressable market for ads on our website and apps. However, we can provide no assurance that we will recoup the revenue impact from MoPub on the expected timeline, or at all.

Our industry is subject to rapid and frequent changes in technology, evolving customer needs and the frequent introduction by our competitors of new and enhanced offerings. We must constantly assess the playing field and determine whether we need to improve or re-allocate resources amongst our existing products and services or create new ones (independently or in conjunction with third parties). Our ability to increase mDAU and engagement, attract content partners, advertisers and platform partners and generate revenue will depend on those decisions. We may introduce significant changes to our existing products and services or develop and introduce new and unproven products and services, including technologies with which we have little or no prior development or operating experience. For example, we are in the early stages of exploring additional potential revenue product opportunities that could, if successful, complement our advertising business in the future, although we do not expect any significant revenue attributable to these opportunities in the near-term and these opportunities may not prove successful at all. We are also continuing our work to increase the stability, performance and scale of our ads platform and our MAPMobile Application Promotion (MAP) product, and such work will take place over multiple quarters, and any positive revenue impact will be gradual in its impact.

If our decisions to invest in product innovations rather than short-term results do not produce the long-term benefits that we expect, and if our new or enhanced products, product features or services fail to engage people on Twitter, content partners and advertisers, we may fail to attract or retain mDAU or to generate sufficient revenue or operating profit to justify our investments, and our business, financial condition and operating results would be adversely impacted.

We believe that maintaining and promoting our brand is critical to increasing mDAU, content partners and advertiser spend. Maintaining and promoting our brand will depend largely on our ability to continue to provide timely, useful, reliable and innovative products and services with a focus on a positive experience on Twitter, which we may not do successfully. We may introduce new features, products, services or terms of service that people on Twitter, content partners, advertisers or platform partners do not like, which may negatively affect our brand. Additionally, the actions of content partners may affect our brand if people do not have a positive experience using third-party applications or websites integrated with Twitter or that make use of Twitter content. We will also continue to experience media, legislative or regulatory scrutiny of our decisions regarding privacy, data protection, security,cybersecurity, content (including our removal of certain influential accounts for violations of our terms of service) and other issues, which may adversely affect our reputation and brand. For example, we previously announced our discovery of content (including some advertisements) displayed on our products that may be relevant to government investigations relating to Russian interference in the 2016 U.S. presidential election, which continues to draw media and regulatory scrutiny of our actions with respect to such content. Our brand may also be negatively affected by the actions of people that are hostile or inappropriate to other people, by accounts impersonating other people, by accounts identified as spam, by use or perceived use, directly or indirectly, of our products or services by people (including governments and government-sponsored actors) to disseminate information that may be viewed as misleading (or intended to manipulate people's opinions), by accounts introducing excessive amounts of spam on our platform, by third parties obtaining control over people's accounts, such as the security breach in July 2020 whereby attackers gained control of certain highly-visible accounts, or by other security or cybersecurity incidents. Maintaining and enhancing our brand may require us to make substantial investments and these investments may not achieve the desired goals.

Additionally, we and our executive leadership receive a high degree of media coverage around the world. Negative publicity about our company or executives, including about the quality and reliability of our products or of content shared on our platform, changes to our products, policies and services, our privacy, data protection, policy enforcement and securitycybersecurity practices (including actions taken or not taken with respect to certain accounts or reports regarding government surveillance or compliance with government legal requests), litigation, regulatory activity, the actions of certain accounts (including actions taken by prominent accounts on our platform or the dissemination of information that may be viewed as misleading or manipulative), even if inaccurate, could adversely affect our reputation. Such negative publicity and reputational harm could adversely affect mDAU and their confidence in and loyalty to our platform and could result in decreased revenue or increased costs to reestablish our brand, which would adversely impact our business, financial condition and operating results.

Our future success and strategy will depend upon our continued ability to identify, hire, develop, motivate and retain highly skilled personnel. We depend on contributions from our employees, and, in particular, our senior management team, to execute efficiently and effectively. We do not have employment agreements other than offer letters with any member of our senior management or other key employees, and we do not maintain key person life insurance for any employee. We also face significant competition for experienced employees, whose talents are in high demand. As a result, we may not be able to retain our existing employees or hire new employees quickly enough to meet our needs.

From time to time, we have also experienced high voluntary attrition, and in those times, the resulting influx of new leaders and other employees has required us to expend time, attention and resources to recruit and retain talent, restructure parts of our organization and train and integrate new employees. In addition, to attract and retain skilled personnel, we have had to offer, and believe we will need to continue to offer, highly competitive compensation packages. We may need to invest significant amounts of cash and equity to attract and retain new employees and we may not realize sufficient return on these investments. In addition, changes to U.S. immigration and work authorization laws and regulations can be significantly affected by political forces and levels of economic activity. Our business may be materially and adversely affected if legislative or administrative changes to immigration or visa laws and regulations impair our hiring processes or projects involving personnel who are not citizens of the country where the work is to be performed. If we are not able to effectively attract and retain employees, we may not be able to innovate or execute quickly on our strategy and our ability to achieve our strategic objectives will be adversely impacted, and our business will be harmed.

We also believe that our culture and core values have been, and will continue to be, a key contributor to our success and our ability to foster the innovation, creativity and teamwork we believe we need to support our operations. We recently announced thatallow most of our employees will be able to work where they feel most productive, whether that is working full-time from home, permanently if they so desirefrom a Twitter office or splitting their time between their home and we expect that we will continue to hire employees that are not located where we have offices or will work from home.a Twitter office. If we fail to effectively manage our hiring needs and successfully integrate our new hires, our efficiency and ability to meet our forecasts, andas well as our culture, employee morale, productivity and retention, could suffer, and our business and operating results would be adversely impacted.

One of the reasons people come to Twitter every day is for real-time information, and our products and the success of our business is dependent upon the ability of people to access the Internet and the proper functioning of the various operating systems, platforms, and services upon which we rely. These systems are provided and controlled by factors outside of our control, including nation-state actors who may suppress or censor our products, and broadband and Internet access marketplace, including incumbent telephone companies, cable companies, mobile communications companies, government-owned service providers, device manufacturers and operating system providers. Any of these actors could take actions that degrade, disrupt or increase the cost of access to our products or services, which would, in turn, negatively impact our business. The adoption or repeal of any laws or regulations that adversely affect the growth, popularity or use of the Internet, including laws or practices limiting Internet neutrality, could decrease the demand for, or the usage of, our products and services, increase our cost of doing business and adversely affect our operating results. For example, access to Twitter is blocked in China and has been intermittently blocked in Turkey in the past.

We also rely on other companies to maintain reliable network systems that provide adequate speed, data capacity and security. We utilize third-party cloud computing services in connection with certain aspects of our business and operations, and any disruption of, or interference with, our use of such cloud services could adversely impact our business and operations. As the Internet continues to experience growth in the number of consumers, frequency of use and amount of data transmitted, the Internet infrastructure that we rely on may be unable to support the demands placed upon it. The failure of the Internet infrastructure that we rely on, even for a short period of time, could undermine our operations and harm our operating results.

Furthermore, these systems, devices or software or services may experience changes, bugs or technical issues that may affect the availability of services or the accessibility of our products. We have experienced, and may in the future experience, service disruptions, outages and other performance problems due to a variety of factors, including infrastructure changes, human or software errors, hardware failure, capacity constraints due to an overwhelming number of people accessing our products and services simultaneously, computer viruses and denial of service or fraud or security attacks. In the past, we have experienced brief service outages during which Twitter.com and Twitter mobile clients were inaccessible as a result, in part, of software misconfigurations. Additionally, although we are investing significantly to improve the capacity, capability and reliability of our infrastructure, we are not currently serving traffic equally through our co-located data centers that support our platform. Accordingly, in the event of a significant issue at the data center supporting most of our network traffic, some of our products and services may become inaccessible to the public or the public may experience difficulties accessing our products and services. Any disruption or failure in our infrastructure could hinder our ability to handle existing or increased traffic on our platform, which could significantly harm our business.

The availability of these services are also dependent upon our relationships with third parties, which may change, including if they change their terms of service or policies that diminish the functionality of our products and services, make it difficult for people to access our content, limit our ability to target or measure the effectiveness of ads, impose fees related to our products or services or give preferential treatment to competitive products or services could adversely affect usage of our products and services. Additionally, some of our mobile carriers have experienced infrastructure issues due to natural disasters, which have caused deliverability errors or poor quality communications with our products. Because a majority of people on Twitter access our products and services through mobile devices, we are particularly dependent on the interoperability of our products and services with mobile devices and operating systems in order to deliver our products and services. We also may not be successful in developing relationships with key participants in the mobile industry or in developing products or services that operate effectively with these operating systems, networks, devices, web browsers and standards. Further, if the number of platforms for which we develop our product expands, it will result in an increase in our operating expenses. In order to deliver high quality products and services, it is important that our products and services work well with a range of operating systems, networks, devices, web browsers and standards that we do not control. In the event that it is difficult for people to access and use our products and services, particularly on their mobile devices, our mDAU growth and engagement could be harmed, and our business and operating results could be adversely impacted.

“Spam” on Twitter refers to a range of abusive activities that are prohibited by our terms of service and is generally defined as unsolicited, repeated actions that negatively impact other people with the general goal of drawing attention to a given account, site, product or idea. This includes posting large numbers of unsolicited mentions of an account, duplicate Tweets, malicious automation, misleading links (e.g., to malware or “click-jacking” pages) or other false or misleading content, and aggressively following and unfollowing accounts, adding accounts to lists, sending invitations, Retweeting and liking Tweets to inappropriately attract attention. Our terms of service prohibit the creation of serial or bulk accounts, both manually or using automation, for disruptive or abusive purposes, such as to Tweet spam or to artificially inflate the popularity of accounts seeking to promote themselves on Twitter. Although we continue to invest resources to reduce spam and fake accounts on Twitter, which includes our investments to improve the health of the public conversation on Twitter, we expect spammers will continue to seek ways to act inappropriately on our platform. In addition, we expect that increases in the number of accounts on our platform will result in increased efforts by spammers to misuse our platform. We continuously combat spam and fake accounts, including by suspending or terminating accounts we believe to be spammers and launching algorithmic changes focused on curbing abusive activities. Our actions to combat spam and fake accounts require significant resources and time. If spam and fake accounts increase on Twitter, this could hurt our reputation for delivering relevant content or reduce mDAU growth rate and mDAU engagement and result in continuing operational cost to us.

Our products and services involve the storage and transmission of people's and advertisers’ information, and security incidents, including those caused by unintentional errors and those intentionally caused by third parties, may expose us to a risk of loss of this information, litigation, increased security costs and potential liability. We and our third-party service providers experience cyber-attacks of varying degrees on a regular basis. We expect to incur significant costs in an effort to detect and prevent security breaches and other security-related incidents, including those that our third-party suppliers and service providers may suffer, and we may face increased costs in the event of an actual or perceived security breach or other security-related incident. In particular, the COVID-19 pandemic is increasinghas increased the opportunities available to criminals, as more companies and individuals work online, and as such, the risk of a cybersecurity incident potentially occurring is increasing.has increased. We cannot provide assurances that our preventative efforts will be successful. If an actual or perceived breach of our security occurs, the market perception of the effectiveness of our security measures could be harmed, people on Twitter and our advertisers may be harmed, lose trust and confidence in us, decrease the use of our products and services or stop using our products and services in their entirety. We may also incur significant legal and financial exposure, including legal claims, higher transaction fees and regulatory fines and penalties. Any of these actions could have a material and adverse effect on our business, reputation and operating results. While our insurance policies include liability coverage for certain of these matters, if we experienced a significant security incident, we could be subject to liability or other damages that exceed our insurance coverage.

Our products and services incorporate complex software and we encourage employees to quickly develop and help us launch new and innovative features. Our software, including any open source software that is incorporated into our code, has contained, and may now or in the future contain, errors, bugs or vulnerabilities. For example, in 2019, we discovered, and took steps to remediate, bugs that primarily affected our legacy MAP product, impacting our ability to target ads and share data with our measurement and ad partners. We also discovered that certain personalization and data settings were not operating as expected. As was the case with these errors, errors in our software code may only be discovered after the product or service has been released. Errors, vulnerabilities, or other design defects within the software on which we rely may result in a negative experience for people on Twitter, partners and advertisers who use our products, delay product introductions or enhancements, result in targeting, measurement, or billing errors, compromise our ability to protect the data of the people on Twitter and/or our intellectual property or lead to reductions in our ability to provide some or all of our services. We have policies and procedures in place to address security as part of our software development, testing, evaluation, and deployment process. Additionally, we have implemented and maintain vulnerability scanning and management policies and procedures, including a bug bounty program. However, these measures may not be sufficient in all cases. Any errors, bugs or vulnerabilities discovered in our code after release could result in damage to our reputation, loss of accounts, loss of content or platform partners, loss of advertisers or advertising revenue or liability for damages or other relief sought in lawsuits, regulatory inquiries or other proceedings, any of which could adversely impact our business and operating results.

Our products operate in conjunction with, and we are dependent upon, third-party products and components across a broad ecosystem. There have been and may continue to be significant attacks on certain third-party providers, and we cannot guarantee that our or our third-party providers’ systems and networks have not been breached or that they do not contain exploitable defects or bugs that could result in a breach of or disruption to our systems and networks or the systems and networks of third parties that support us and our services. If there is a security vulnerability, error, or other bug in one of these third-party products or components and if there is a security exploit targeting them, we could face increased costs, liability claims, reduced revenue, or harm to our reputation or competitive position. The natural sunsetting of third-party products and operating systems that we use requires that our infrastructure teams reallocate time and attention to migration and updates, during which period potential security vulnerabilities could be exploited.

Unauthorized parties may also gain access to Twitter handles and passwords without attacking Twitter directly and, instead, access people’s accounts by using credential information from other recent breaches, using malware on victim machines that are stealing passwords for all sites, or a combination of both. In addition, some of our developers or other partners, such as third-party applications to which people have given permission to Tweet on their behalf, may receive or store information provided by us or by people on Twitter through mobile or web applications integrated with us. If these third parties or developers fail to adopt or adhere to adequate data security practices, or in the event of a breach of their networks, our data or data of people on Twitter may be improperly accessed, used or disclosed. Unauthorized parties have obtained, and may in the future obtain, access to our data, data of people on Twitter or our advertisers’ data. Any systems failure or actual or perceived compromise of our security that results in the unauthorized access to or release of data of people on Twitter or our advertisers’ data, such as credit card data, could significantly limit the adoption of our products and services, as well as harm our reputation and brand and, therefore, our business.

Our security measures may also be breached due to employee error, malfeasance or otherwise. Additionally, outside parties may attempt to fraudulently induce employees, people on Twitter, or advertisers to disclose sensitive information in order to gain access to our data, data of people on Twitter or advertisers’ data, or may otherwise obtain access to such data or accounts. Since people on Twitter and our advertisers may use Twitter to establish and maintain online identities, unauthorized communications from Twitter accounts that have been compromised may damage their personal security, reputations and brands as well as our reputation and brand. Because the techniques used to obtain unauthorized access, disable or degrade service or sabotage systems change frequently and often are not recognized until launched against a target, we may be unable to anticipate these techniques or to implement adequate preventative measures.

For example, in July 2020, we became aware of what we believe to be a coordinated social engineering attack by people who successfully targeted one or more of our employees with access to internal systems and tools. The attackers used this access to target a small group of accounts (130) and to gain control of a subset of these accounts and send Tweets from those accounts and access non-public information relating to at least some of those accounts. This security breach may have harmed the people and accounts affected by it. It may also impact the market perception of the effectiveness of our security measures, and people may lose trust and confidence in us, decrease the use of our products and services or stop using our products and services in their entirety. It may also result in damage to our reputation, loss of accounts, loss of content or platform partners, loss of advertisers or advertising revenue, or legal and financial exposure, including legal claims, regulatory inquiries or other proceedings. Any of these effects could have a material and adverse impact on our business, reputation and operating results.

We have offices and employees around the world and our products and services are available in multiple languages. However, our ability to manage our business, monetize our products and services and conduct our operations internationally requires considerable management attention and resources and is subject to the particular challenges of supporting a rapidly growing business in an environment of multiple languages, cultures, customs, legal and regulatory systems, alternative dispute systems and commercial markets. Our international operations have required and will continue to require us to invest significant funds and other resources. Operating internationally subjects us to new risks and may increase risks that we currently face, including risks associated with:

If our revenue from our international operations, and particularly from our operations in the countries and regions where we have focused our spending, does not exceed the expense of establishing and maintaining these operations, our business and operating results will suffer. In addition, mDAU may grow more rapidly than revenue in international regions where our monetization of our products and services is not as developed. If we are unable to successfully expand our business, manage the complexity of our global operations or monetize our products and services internationally, it could adversely impact our business, financial condition and operating results.

In 2020, as well as other periods in the past,While we have incurred significant operating losses. While we werebeen profitable on a generally accepted accounting principles in the United States (GAAP) basis in 2018, 2019, and the third and fourth quarters of 2020,at times, our quarterly operating results have fluctuated in the past and will fluctuate in the future. As a result, our past quarterly operating results are not necessarily indicators of future performance. Our operating results in any given quarter have been and can be influenced by numerous factors, many of which we are unable to predict or are outside of our control, including:

Given the rapidly evolving markets in which we compete, our historical operating results may not be useful to you in predicting our future operating results. If our revenue growth rate slows, we expect that the seasonality in our business may become more pronounced and may in the future cause our operating results to fluctuate. For example, advertising spending is traditionally seasonally strong in the fourth quarter of each year, and we believe that this seasonality affects our quarterly results, which generally reflect higher sequential advertising revenue growth from the third to fourth quarter compared to sequential advertising revenue growth from the fourth quarter to the subsequent first quarter. Additionally, certain new revenue products or product features may carry higher costs relative to our other products, which may decrease our margins, and we may incur increased costs to scale our operations if mDAU and engagement on our platform increase. If we are unable to generate adequate revenue growth and to manage our expenses, we may incur significant losses in future periods and may not be able to maintain profitability.

We calculate our mDAU using internal company data that has not been independently verified. While these numbers are based on what we believe to be reasonable calculations for the applicable period of measurement, there are inherent challenges in measuring mDAU and mDAU engagement. For example, there are a number of false or spam accounts in existence on our platform. We estimate that the average of false or spam accounts during the fourth quarter of 20202021 continued to represent fewer than 5% of our mDAU during the quarter. However, this estimate is based on an internal review of a sample of accounts and we apply significant judgment in making this determination. As such, our estimation of false or spam accounts may not accurately represent the actual number of such accounts, and the actual number of false or spam accounts could be higher than we have currently estimated. We are continually seeking to improve our ability to estimate the total number of spam accounts and eliminate them from the calculation of our mDAU, but we otherwise treat multiple accounts held by a single person or organization as multiple accounts for purposes of calculating our mDAU because we permit people and organizations to have more than one account. Additionally, some accounts used by organizations are used by many people within the organization. As such, the calculations of our mDAU may not accurately reflect the actual number of people or organizations using our platform. We regularly review and may adjust our processes for calculating our internal metrics to improve their accuracy. Our measures of mDAU growth and engagement may differ from estimates published by third parties or from similarly-titled metrics of our competitors due to differences in methodology. If advertisers, content or platform partners or investors do not perceive our metrics to be accurate representations of our total accounts or mDAU engagement, or if we discover material inaccuracies in our metrics, our reputation may be harmed and content partners, advertisers and platform partners may be less willing to allocate their budgets or resources to our products and services, which could negatively affect our business and operating results. Further, as our business develops, we may revise or cease reporting metrics if we determine that such metrics are no longer accurate or appropriate measures of our performance. If investors, analysts or customers do not believe our reported measures, such as mDAU, are sufficient or accurately reflect our business, we may receive negative publicity and our operating results may be adversely impacted.

A significant natural disaster, such as the COVID-19 pandemic or an earthquake, fire, flood or significant power outage could have a material adverse impact on our business, operating results, and financial condition. For example, the COVID-19 pandemic has led to certain business disruptions, as described in our other risk factors, including travel bans and restrictions, shelter-in-place orders and the postponement or cancellation orof major events, which have adversely affected demand for our advertising products and the economy as a whole, and which may continue to have an adverse effect on our business, financial condition and operating results. Our headquarters are locatedresults in the future. We have offices and a significant number of employees in the San Francisco Bay Area, a region known for seismic activity. Additionally, despite any precautions we may take, the occurrence of a natural disaster or other unanticipated problems at our data centers could result in lengthy interruptions in our services. In addition, our employees, offices, and infrastructure have recently been the subject of increased threats by extremists. Acts of terrorism and other geo-political unrest could cause disruptions in our business. All of the aforementioned risks may be further increased if our disaster recovery plans prove to be inadequate. We have implemented a disaster recovery program, which allows us to move production to a back-up data center in the event of a catastrophe. Although this program is functional, we do not currently serve network traffic equally from each data center, so if our primary data center shuts down, there will be a period of time that our products or services, or certain of our products or services, will remain inaccessible or people may experience severe issues accessing our products and services. We do not carry business interruption insurance sufficient to compensate us for the potentially significant losses, including the potential harm to our business that may result from interruptions in our ability to provide our products and services. Any such natural disaster or man-made problem could adversely impact our business, financial condition and operating results.

As accounts generate more content, including photos and videos hosted by Twitter, we may be required to expand and adapt our technology and infrastructure to continue to reliably store, serve and analyze this content. It may become increasingly difficult to maintain and improve the performance of our products and services, especially during peak usage times, as our products and services become more complex and our account traffic increases. In addition, because we lease our data center facilities, we cannot be assured that we will be able to expand our data center infrastructure to meet demand in a timely manner, or on favorable economic terms. If people are unable to access Twitter or we are not able to make information available rapidly on Twitter, people may seek other channels to obtain the information, and may not return to Twitter or use Twitter as often in the future, or at all. This would negatively impact our ability to attract new people to Twitter, content partners and advertisers and increase the frequency of people returning to Twitter. We expect to continue to make significant investments to maintain and improve the capacity, capability and reliability of our infrastructure. To the extent that we do not effectively address capacity constraints, upgrade our systems as needed and continually develop our technology and infrastructure to accommodate actual and anticipated changes in technology, our business and operating results may be harmed.

We continue to scale the capacity of, and enhance the capability and reliability of, our infrastructure to support mDAU growth and increased activity on our platform. We expect that investments and expenses associated with our infrastructure will continue to grow, including the expansion and improvement of our data center operations and related operating costs, additional servers and networking equipment to increase the capacity of our infrastructure, increased utilization of third-party cloud computing and associated costs thereof, increased bandwidth costs and costs to secure our customers’ data. The improvement of our infrastructure requires a significant investment of our management’s time and our financial resources. If we fail to efficiently scale and manage our infrastructure, our business, financial condition and operating results would be adversely impacted.

Intellectual property rights are important assets of our business and we seek protection for such rights as appropriate. To establish and protect our trade secrets, trademarks, copyrights, and patents as well as restrictions in confidentiality, license and intellectual property assignment agreements we enter into with our employees, consultants and third parties. Various circumstances and events outside of our control, however, pose threats to our intellectual property rights. We may fail to obtain effective intellectual property protection, effective intellectual property protection may not be available in every country in which our products and services are available, or such laws may provide only limited protection. Also, the efforts we have taken to protect our intellectual property rights may not be sufficient or effective, and any of our intellectual property rights may be challenged, circumvented, infringed or misappropriated which could result in them being narrowed in scope or declared invalid or unenforceable. There can be no assurance our intellectual property rights will be sufficient to protect against others offering products or services that are substantially similar to ours and compete with our business.

We rely on restrictions on the use and disclosure of our trade secrets and other proprietary information contained in agreements we sign with our employees, contractors, and other third parties to limit and control access to and disclosure of our trade secrets and confidential information. These agreements may be breached, or this intellectual property may otherwise be disclosed or become known to our competitors, including through hacking or theft, which could cause us to lose any competitive advantage resulting from these trade secrets and proprietary information.

We are pursuing registration of trademarks and domain names in the United States and in certain jurisdictions outside of the United States. Effective protection of trademarks and domain names is expensive and difficult to maintain, both in terms of application and registration costs as well as the costs of defending and enforcing those rights. We may be required to protect our rights in an increasing number of countries, a process that is expensive and may not be successful or which we may not pursue in every country in which our products and services are distributed or made available.

We are party to numerous agreements that grant licenses to third parties to use our intellectual property. For example, many third parties distribute their content through Twitter, or embed Twitter content in their applications or on their websites, and make use of our trademarks in connection with their services. We have a policy designed to assist third parties in the proper use of our trademarks, and an internal team dedicated to enforcing this policy and protecting our brand. This team routinely reviews reports of improper and unauthorized use of the Twitter trademarks and issues takedown notices or initiates discussions with the third parties to correct the issues. However, there can be no assurance that we will be able to protect against the unauthorized use of our brand or trademarks. If the licensees of our trademarks are not using our trademarks properly and we fail to maintain and enforce our trademark rights, we may limit our ability to protect our trademarks which could result in diminishing the value of our brand or in our trademarks being declared invalid or unenforceable. There is also a risk that one or more of our trademarks could become generic, which could result in such trademark being declared invalid or unenforceable. For example, there is a risk that the word “Tweet” could become so commonly used that it becomes synonymous with any short comment posted publicly on the Internet, and if this happens, we could lose protection of this trademark.

We also seek to obtain patent protection for some of our technology. We may be unable to obtain patent protection for our technologies. Even if patents are issued from our patent applications, which is not certain, our existing patents, and any patents that may be issued in the future, may not provide us with competitive advantages or distinguish our products and services from those of our competitors. In addition, any patents may be contested, circumvented, or found unenforceable or invalid, and we may not be able to prevent third parties from infringing or otherwise violating them. Effective protection of patent rights is expensive and difficult to maintain, both in terms of application and maintenance costs, as well as the costs of defending and enforcing those rights.

Our Innovator’s Patent Agreement, or IPA, also can limit our ability to prevent infringement of our patents. In May 2013, we implemented the IPA, which we enter into with our employees and consultants, including our founders. The IPA, which applies to our current and future patents, allows us to assert our patents defensively. The IPA also allows us to assert our patents offensively with the permission of the inventors of the applicable patent. Under the IPA, an assertion of claims is considered to be for a defensive purpose if the claims are asserted: (i) against an entity that has filed, maintained, threatened or voluntarily participated in a patent infringement lawsuit against us or any people on Twitter, or any of our affiliates, customers, suppliers or distributors; (ii) against an entity that has used its patents offensively against any other party in the past ten years, so long as the entity has not instituted the patent infringement lawsuit defensively in response to a patent litigation threat against the entity; or (iii) otherwise to deter a patent litigation threat against us or people on Twitter, or any of our affiliates, customers, suppliers or distributors. In addition, the IPA provides that the above limitations apply to any future owner or exclusive licensee of any of our patents, which could limit our ability to sell or license our patents to third parties. In this case, while we may be able to claim protection of our intellectual property under other rights (such as trade secrets or contractual obligations with our employees not to disclose or use confidential information), we may be unable to assert our patent rights against third parties that we believe are infringing our patents, even if such third parties are developing products and services that compete with our products and services. For example, in the event that an inventor of one of our patents goes to work for another company and that company uses the inventor’s patented invention to compete with us, we would not be able to assert that patent against such other company unless the assertion of the patent right is for a defensive purpose since it would be unlikely the employee would consent to offensive use of the patent against his or her current employer. In such event, we would need to rely on trade secret protection or the contractual obligation of the inventor to us not to disclose or use our confidential information. In addition, the terms of the IPA could affect our ability to monetize our intellectual property portfolio.

Significant impairments of our intellectual property rights, and limitations on our ability to assert our intellectual property rights against others, could harm our business and our ability to compete.

Also, obtaining, maintaining and enforcing our intellectual property rights is costly and time consuming. Any increase in the unauthorized use of our intellectual property would adversely impact our business, financial condition and operating results.

We use open source software in our products and services and will use open source software in the future. In addition, we regularly contribute software source code to open source projects under open source licenses or release internal software projects under open source licenses, and anticipate doing so in the future. The terms of many open source licenses to which we are subject have not been interpreted by U.S. or foreign courts, and there is a risk that open source software licenses could be construed in a manner that imposes unanticipated conditions or restrictions on our ability to provide or distribute our products or services. Additionally, under some open source licenses, if we combine our proprietary software with open source software in a certain manner, third parties may claim ownership of, or demand release of, the open source software or derivative works that we developed using such software, which could include our proprietary source code. Such third parties may also seek to enforce the terms of the applicable open source license through litigation which, if successful, could require us to make our proprietary software source code freely available, purchase a costly license or cease offering the implicated products or services unless and until we can re-engineer them to avoid infringement. This re-engineering process could require significant additional research and development resources, and we may not be able to complete it successfully. In addition to risks related to open source license requirements, use of certain open source software may pose greater risks than use of third-party commercial software, since open source licensors generally do not provide warranties or controls on the origin of software. Any of these risks could be difficult to eliminate or manage, and, if not addressed, could adversely impact our business, financial condition and operating results.

Companies in the internet, technology and media industries are subject to litigation based on allegations of infringement, misappropriation or other violations of intellectual property rights. Many companies in these industries, including many of our competitors, have substantially larger patent and intellectual property portfolios than we do, which could make us a target for litigation as we may not be able to assert counterclaims against parties that sue us for patent, or other intellectual property infringement. In addition, various “non-practicing entities” that own patents and other intellectual property rights often attempt to assert claims in order to extract value from technology companies. From time to time we receive claims from third parties which allege that we have infringed upon their intellectual property rights. Further, from time to time we may introduce new products, product features and services, including in areas where we currently do not have an offering, which could increase our exposure to patent and other intellectual property claims from competitors and non-practicing entities. In addition, although our standard terms and conditions for our Promoted Products and public APIs do not provide advertisers and platform partners with indemnification for intellectual property claims against them, some of our agreements with advertisers, content partners, platform partners and data partners require us to indemnify them for certain intellectual property claims against them, which could require us to incur considerable costs in defending such claims, and may require us to pay significant damages in the event of an adverse ruling. Such advertisers, content partners, platform partners and data partners may also discontinue use of our products, services and technologies as a result of injunctions or otherwise, which could result in loss of revenue and adversely impact our business.

We presently are involved in a number of intellectual property lawsuits, and as we face increasing competition and develop new products, we expect the number of patent and other intellectual property claims against us may grow. There may be intellectual property or other rights held by others, including issued or pending patents, that cover significant aspects of our products and services, and we cannot be sure that we are not infringing or violating, and have not infringed or violated, any third-party intellectual property rights or that we will not be held to have done so or be accused of doing so in the future. Any claim or litigation alleging that we have infringed or otherwise violated intellectual property or other rights of third parties, with or without merit, and whether or not settled out of court or determined in our favor, could be time-consuming and costly to address and resolve, and could divert the time and attention of our management and technical personnel. Some of our competitors have substantially greater resources than we do and are able to sustain the costs of complex intellectual property litigation to a greater degree and for longer periods of time than we could. The outcome of any litigation is inherently uncertain, and there can be no assurances that favorable final outcomes will be obtained in all cases. In addition, plaintiffs may seek, and we may become subject to, preliminary or provisional rulings in the course of any such litigation, including potential preliminary injunctions requiring us to cease some or all of our operations. We may decide to settle such lawsuits and disputes on terms that are unfavorable to us. Similarly, if any litigation to which we are a party is resolved adversely, we may be subject to an unfavorable judgment that may not be reversed upon appeal. The terms of such a settlement or judgment may require us to cease some or all of our operations or pay substantial amounts to the other party. In addition, we may have to seek a license to continue practices found to be in violation of a third-party’s rights. If we are required, or choose to enter into royalty or licensing arrangements, such arrangements may not be available on reasonable terms, or at all, and may significantly increase our operating costs and expenses. As a result, we may also be required to develop or procure alternative non-infringing technology, which could require significant effort and expense or discontinue use of the technology. An unfavorable resolution of the disputes and litigation referred to above would adversely impact our business, financial condition and operating results.

We are subject to a variety of laws and regulations in the United States and abroad that involve matters central to our business, including privacy, data protection, data security,cybersecurity, advertising, rights of publicity, content regulation, intellectual property, competition, protection of minors, consumer protection, provision of online payment services and credit card processing, securities law compliance, and taxation.taxation, as well as laws and regulations regarding the environment and climate change. For example, new content regulation laws may affect our ability to operate in certain markets and/or subject us to significant fines or penalties. Compliance with these laws may be onerous and/or inconsistent with our work to serve the public conversation. Many of these laws and regulations are still evolving and being tested in courts and new laws and regulations are being proposed. As a result, it is possible that these laws and regulations may be interpreted and applied in a manner that is inconsistent from country to country and inconsistent with our current policies and practices and in ways that could harm our business, particularly in the new and rapidly evolving industry in which we operate. Additionally, the introduction of new products or services may subject us to additional laws and regulations.

From time to time, governments, regulators and others have expressed concerns about whether our products, services or practices compromise the privacy or data protection rights of the people on Twitter and others. While we strive to comply with applicable laws and regulations relating to privacy, data protection and data security,cybersecurity, our privacy policies and other obligations we may have with respect to privacy, data protection and data security,cybersecurity, the failure or perceived failure to comply may result, and in some cases has resulted, in inquiries and other proceedings or actions against us by governments, regulators or others. A number of proposals have recently been adopted or are currently pending before federal, state and foreign legislative and regulatory bodies that could significantly affect our business. For example, the California Consumer Privacy Act (CCPA) went into effect on January 1, 2020. The CCPA requires, among other things, covered companies to provide new disclosures to California consumers and afford such consumers new abilitiesthe ability to opt-out of certain sales of personal information. Similar legislation has been proposed or adopted in other states. Additionally, on November 3, 2020, a ballot initiative in California passed a new privacy law, the California Privacy Rights Act (CPRA). created obligations relating to consumer data beginning on January 1, 2022, with implementing regulations expected on or before July 1, 2022, and enforcement beginning July 1, 2023. On March 2, 2021, Virginia enacted the Virginia Consumer Data Protection Act, or CDPA, a comprehensive privacy statute that becomes effective on January 1, 2023, and on June 8, 2021, Colorado enacted the Colorado Privacy Act, or CPA, which takes effect on July 1, 2023. The CPRA would significantly modifyCDPA and CPA share similarities with the CCPA, potentially resultingCPRA, and legislation proposed in further uncertainty and requiring us to incur additional costs and expenses.other states. Aspects of the CCPA, the CPRA and these other state laws and regulations, as well as their enforcement, remain unclear, and we may be required to modify our practices in an effort to comply with them. Moreover, foreign data protection, privacy, cybersecurity, and other laws and regulations are often more restrictive or burdensome than those in the United States. For example, the GDPR imposes stringent operational requirements for entities processing personal information and significant penalties for non-compliance, including fines of up to €20 million or 4% of total worldwide revenue, whichever is higher. Additionally, we have historically relied upon a variety of legal bases to transfer certain personal information outside of the European Economic Area (EEA), including the EU-U.S. Privacy Shield Framework, the Swiss-U.S. Privacy Shield Framework, and EU Standard Contractual Clauses (SCCs). These legal bases all have been, and may be, the subject of legal challenges and on July 16, 2020, the Court of Justice of the European Union (CJEU) invalidated the U.S.-EU Privacy Shield framework and imposed additional obligations on companies when relying on the SCCs. This CJEU decisionThe Swiss-U.S. Privacy Shield framework subsequently was invalidated by the Swiss Federal Data Protection and Information Commissioner. These developments may result in different European Economic AreaEEA data protection regulators applying differing standards for, or require ad hoc verification of measures taken with respect to, certain data flows. The CJEU’s decision, willthe European Commission’s issuance of new SCCs in June 2021, the use of which was required in connection with new contracts and new personal data processing operations as of September 27, 2021, continued guidance from the European Commission and European Data Protection Board (EDPB) , and other developments with regard to cross-border data transfers may require us to take additional steps to legitimize impacted personal data transfers, and we may find it necessary or desirable to modify our data handling practices in connection with this decisionthese or future legal challenges or other developments relating to cross-border data transfers. This could result in additional contractual negotiations and increased costs of compliance and limitations on our customers, vendors, and us. This CJEU decision and related developments, or future legal challenges or other developments, also could result in us being required to implement duplicative, and potentially expensive, information technology infrastructure and business operations in Europe or could limit our ability to collect or process personal information in Europe, and may serve as a basis for our personal data handling practices, or those of our customers and vendors, to be challenged. Moreover, the GDPR and other similar regulations require companies to give specific types of notice and in some cases seek consent from consumers and other data subjects before collecting or using their data for certain purposes, including some marketing activities. In addition to the GDPR, the European Commission has another draft regulation in the approval process that focuses on a person’s right to conduct a private life. The proposed legislation, known as the Regulation of Privacy and Electronic Communications (ePrivacy Regulation), would replace the current ePrivacy Directive. Originally planned to be adopted and implemented at the same time as the GDPR, the ePrivacy Regulation is still being negotiated. Most recently, on February 10, 2021, the Council of the EU agreed on its version of the draft ePrivacy Regulation. If adopted, the earliest date for entry into force is in 2023, with broad potential impacts on the use of internet-based services and tracking technologies, such as cookies. Aspects of the ePrivacy Regulation remain for negotiation between the European Commission and the Council. Any of these changes or other developments with respect to EU data protection law could disrupt our business and otherwise adversely impact our business, financial condition and operating results.

Further, the UK officially left the EU in 2020 (often referred to as "Brexit")Brexit). The full effect of Brexit will depend on agreements, if any, the UK makes to retain access to EU markets.remains uncertain, but Brexit creates economic and legal uncertainty in the region and could adversely affect the tax, currency, operational, legal and regulatory regimes to which our business is subject, including with respect to privacy and data protection. Brexit may adversely affect our revenues and subject us to new regulatory costs and challenges, in addition to other adverse effects that we are unable effectively to anticipate. The UK has implemented a Data Protection Act, effective in May 2018 and statutorily amended in 2019,legislation referred to as the UK GDPR, that substantially implementsimplement the GDPR, with penalties for noncompliance of up to the greater of £17.5 million or four percent of worldwide revenues. Brexit has, however, createdOn June 28, 2021, the European Commission adopted an adequacy decision with respect to the UK, which allows cross-border data transfers from the EEA to the UK for a four-year period, subject to renewal and the potential for earlier modification or termination. Nevertheless, substantial uncertainty with regard to theremains regarding future regulation of data protection in the UK, and requirements for data transfers between the UK and the EU and other jurisdictions. For example, the EU-UK Trade and Cooperation Agreement provides for a transition period of four months, subject to a potential two-month extension, in which the European Commission will, subject to certain exceptions that may result in termination of such transition period, continue to treat the UK as if it remained an EU member state with respect to personal data transfers. The UK may thereafter be considered a “third country” under the GDPR, with transfers of personal data from the EU to the UK needing to be made pursuant to GDPR-compliant safeguards unless the European Commission adopts an adequacy decision with respect to the UK. With substantial uncertainty over the interpretation and application of how the UK will approach and address the GDPR following the transition period, we may face challenges and significant costs and expenses in addressing applicable requirements and making necessary changes to our policies and practices, and may incur significant costs and expenses in an effort to do so.practices.

Legislative changes in the United States, at both the federal and state level, could impose new obligations in areas such as moderation of content posted on our platform by third parties, including with respect to requests for removal based on claims of copyright. Further, there are various Executive and Congressional efforts to restrict the scope of the protections from legal liability for content moderation decisions and third-party content posted on online platforms that are currently available to online platforms under Section 230 of the Communications Decency Act, and our current protections from liability for content moderation decisions and third-party content posted on our platform in the United States could decrease or change, potentially resulting in increased liability for content moderation decisions and third-party content posted on our platform and higher litigation costs. Additionally, recent amendments to U.S. patent laws may affect the ability of companies, including us, to protect their innovations and defend against claims of patent infringement.

In April 2019, the EU passed the Directive on Copyright in the Digital Single Market (the EU Copyright Directive), which expands the liability of online platforms for third-party content posted on the platform. Each EU member state hashad two years to implement it.it, with a deadline of June 7, 2021, though implementation has been delayed in several EU member states. The EU Copyright Directive may increase our costs of operations, our liability for third-party content posted on our platform, and our litigation costs.

Additionally, we have relationships with third parties that perform a variety of functions such as payments processing, tokenization, vaulting, currency conversion, fraud prevention and data securitycybersecurity audits. The laws and regulations related to online payments and other activities of these third parties, including those relating to the processing of data, are complex, subject to change, and vary across different jurisdictions in the United States and globally. As a result, we may be required to spend significant time, effort and expense to comply with applicable laws and regulations. Any failure or claim of our failure to comply, or any failure or claim of failure by the above-mentioned third parties to comply, could increase our costs or could result in liabilities. Additionally, because we accept payment via credit cards, we are subject to global payments industry operating rules and certification requirements governed by the PCI Security Standards Council, including the Payment Card Industry Data Security Standard. Any failure by us to comply with these operating rules and certification requirements also may result in costs and liabilities and may result in us losing our ability to accept certain payment cards. We recently announced new subscription and paid features on Twitter. Depending on how these products and features evolve, we may also be subject to other laws and regulations related to online payments, money transmission, prepaid access, electronic fund transfers or other financial laws or regulations, and we may need to register as a money services business with the U.S. Treasury Department and obtain state money transmitter licenses in the United States and an Electronic Money (E-money) license in the EEA to permit us to conduct certain activities. These licenses and other legal requirements will generally require us to demonstrate compliance with many domestic and foreign laws in these areas, including anti-money laundering, counter-terrorist financing, government sanctions, cybersecurity, privacy, and consumer protection laws, and failure to do so may limit our ability to offer these products and features as they evolve.

The U.S. and foreign laws and regulations described above, as well as any associated inquiries or investigations or any other regulatory actions, may be onerous and costly to comply with and may be inconsistent from jurisdiction to jurisdiction, further increasing the cost of compliance and doing business. Any such costs may delay or impede the development of new products and services, result in negative publicity, increase our operating costs, require significant management time and attention, and subject us to remedies that may result in a loss of mDAU or advertisers and otherwise harm our business, including fines or demands or orders that we modify or cease existing business practices.

We currently allow use of our platform without the collection of extensive personal information. We may experience additional pressure to expand our collection of personal information in order to comply with new and additional legal or regulatory demands or we may independently decide to do so. If we obtain such additional personal information, we may be subject to additional legal or regulatory obligations.

From time to time we notify the Irish Data Protection Commission and other regulators of certain personal data breaches and privacy, cybersecurity or data protection issues, and are subject to inquiries and investigations regarding various aspects of our regulatory compliance. We are currently the subject of inquiries by the Irish Data Protection Commission with respect to our compliance with the GDPR. In the past, we have been subject to regulatory investigations and orders, and we expect to continue to be subject to regulatory scrutiny as our business grows and awareness of our brand increases.

In March 2011, to resolve an investigation into various incidents, we entered into a consent order with the FTC that, among other things, required us to establish an information security program designed to protect non-public consumer information and also requires that we obtain biennial independent security assessments. The obligations under the consent order remain in effect until the later of March 2, 2031, or the date 20 years after the date, if any, on which the U.S. government or the FTC files a complaint in federal court alleging any violation of the order. We expect to continue to be the subject of regulatory inquiries, investigations and audits in the future by the FTC and other regulators around the world. Violation of existing or future regulatory orders, settlements or consent decrees could subject us to substantial fines, penalties and costs that would adversely impact our financial condition and operating results. For example, on July 28, 2020, we received a draft complaint from the FTC alleging violations of the 2011 consent order with the FTC and the FTC Act. The allegations relate to our use of phone number and/or email address data provided for safety and security purposes for targeted advertising during periods between 2013 and 2019. We estimate that the range of probable loss in this matter is $150.0 million to $250.0 million. The matter remains unresolved, and there can be no assurance as to the timing or the terms of any final outcome.

It is possible that a regulatory inquiry, investigation or audit could cause us to incur substantial fines and costs, result in reputational harm, prevent us from offering certain products, services, features or functionalities, require us to change our policies or practices, divert management and other resources from our business, or otherwise materially and adversely impact our business, financial condition and operating results.

We have faced and will continue to face claims relating to content that is published or made available through our products and services or third-party products or services. In particular, the nature of our business exposes us to claims related to defamation, intellectual property rights, rights of publicity and privacy, illegal content, misinformation, content regulation and personal injury torts. The laws relating to the liability of providers of online products or services for activities of the people who use them remains somewhat unsettled, both within the United States and internationally. For example, there are various Executive and Congressional efforts to restrict the scope of the protections from legal liability for content moderation decisions and third-party content posted on online platforms that are currently available to online platforms under Section 230 of the Communications Decency Act, and our current protections from liability for content moderation decisions and third-party content posted on our platform in the United States could decrease or change, potentially resulting in increased liability for content moderation decisions and third-party content posted on our platform and higher litigation costs. This risk may be enhanced in certain jurisdictions outside the United States where we may be less protected under local laws than we are in the United States. For example, we are subject to legislation in Germany that may impose significant fines for failure to comply with certain content removal and disclosure obligations. Other countries, including Brazil, Turkey, Singapore, India, Australia, and the United Kingdom, have implemented or are considering similar legislation imposing penalties for failure to remove certain types of content. In addition, the public nature of communications on our platform exposes us to risks arising from the creation of impersonation accounts intended to be attributed to people on Twitter or our advertisers. We could incur significant costs investigating and defending these claims. If we incur material costs or liability as a result of these occurrences, our business, financial condition and operating results would be adversely impacted.

As a public company, we are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, or the Exchange Act, the Sarbanes-Oxley Act of 2002, as amended, or the Sarbanes-Oxley Act, and the listing standards of the New York Stock Exchange. The Sarbanes-Oxley Act requires, among other things, that we maintain effective disclosure controls and procedures and internal control over financial reporting. In order to maintain and improve the effectiveness of our disclosure controls and procedures and internal control over financial reporting, we have expended, and anticipate that we will continue to expend, significant resources, including accounting-related costs and significant management oversight.

Any failure to develop or maintain effective controls, or any difficulties encountered in their implementation or improvement, could cause us to be subject to one or more investigations or enforcement actions by state or federal regulatory agencies, stockholder lawsuits or other adverse actions requiring us to incur defense costs, pay fines, settlements or judgments. Any such failures could also cause investors to lose confidence in our reported financial and other information, which would likely have a negative effect on the trading price of our common stock. In addition, if we are unable to continue to meet these requirements, we may not be able to remain listed on the New York Stock Exchange.

Our success will depend, in part, on our ability to expand our products, product features and services, and grow our business in response to changing technologies, demands of people on Twitter and our advertisers and competitive pressures. In some circumstances, we may determine to do so through the acquisition of complementary businesses and technologies rather than through internal development, including, for example, our acquisitions of CrossInstall, a demand side platform, and MoPub, a mobile-focused advertising exchange.development. The identification of suitable acquisition candidates can be difficult, time-consuming and costly, and we may not be able to successfully complete identified acquisitions. The risks we face in connection with acquisitions include:

Our failure to address these risks or other problems encountered in connection with our past or future acquisitions and investments could cause us to fail to realize the anticipated benefits of these acquisitions or investments, cause us to incur unanticipated liabilities, and harm our business generally. Future acquisitions could also result in dilutive issuances of our equity securities, the incurrence of debt, contingent liabilities, amortization expenses, incremental operating expenses or the impairment of goodwill,assets, any of which could adversely impact our financial condition and operating results.

We also make investments in privately-held companies in furtherance of our strategic objectives. Many of the instruments in which we invest are non-marketable at the time of our initial investment. We may not realize a return and may recognize a loss on such investments.

In certain cases, we have also divested or stopped investing in certain businesses or products, including products that we acquired. In these cases, we have needed toacquired, and we may continue to do so. For example, in January 2022, we completed the future needsale of our MoPub business. The sale of a business or product line may require us to restructure operations and/or terminate employees, and could expose us to unanticipated ongoing obligations and liabilities, including as a result of our indemnification obligations. Additionally, such transactions could disrupt our customer, supplier and/or employee relationships and divert management and our employees’ time and attention. During the pendency of a divestiture, we may be subject to risks related to a decline in the business, loss of employees, customers, or suppliers, and that the transaction may not close, which could have a material and adverse effect on the business to be divested and on us. If a divestiture is not completed for any reason, we may not be able to find a buyer on the same terms. If we decide to sell a business or product line, we may experience difficulty separating out portions of or entire businesses, incur other expenses. Weadditional expenses and potential loss of revenue or experience a negative impact on margins. Ultimately, we may experience harm to our financial results, including loss of revenue, and we may not realize the expected benefits and cost savings of these actions and our operating results may be adversely impacted.

In 2014, we issued $954.0 million in aggregate principal amount of 1.00% convertible senior notes due 2021, or the 2021 Notes. In 2018, we issued an additional $1.15 billion in aggregate principal amount of 0.25% convertible senior notes due 2024, or the 2024 Notes. In 2019, we issued $700.0 million in aggregate principal amount of 3.875% senior notes due 2027, which we refer to asor the 2027 Notes. In March 2020, we issued $1.0 billion in aggregate principal amount of 0.375% convertible senior notes due 2025, or the 2025 Notes. In March 2021, we issued $1.44 billion in aggregate principal amount of 0% convertible senior notes due 2026, or the 2026 Notes. We refer to the 20212024 Notes, the 20242025 Notes, and the 20252026 Notes as the Convertible Notes, and we refer to the Convertible Notes and the 2027 Notes as the Notes. As of December 31, 2020,2021, we had $3.80$4.29 billion in aggregate principal amount of Notes outstanding Notes. As of December 31, 2020, we also hadand an undrawn unsecured revolving credit facility providing for loans in the aggregate principal amount of $500.0 million.

Our debt obligations could adversely impact us. For example, these obligations could:

Our income tax obligations are based in part on our corporate operating structure, including the manner in which we develop, value, manage, protect and use our intellectual property and the scope of our international operations. We are subject to review and audit by tax authorities in the United States (federal and state), Ireland, and other foreign jurisdictions and the laws in those jurisdictions are subject to interpretation. Tax authorities may disagree with and challenge some of the positions we have taken and any adverse outcome of such an audit could have a negative effect on our financial position and operating results. In addition, our future income taxes could be adversely affected by earnings being lower than anticipated in jurisdictions that have lower statutory tax rates and higher than anticipated in jurisdictions that have higher statutory tax rates, by changes in the valuation of our deferred tax assets and liabilities, or by changes in tax laws, regulations or accounting principles, as well as certain discrete items. For example, the legislation commonly referred to as the 2017 Tax Cuts and Jobs Act (the Tax Act) significantly affected U.S. tax law by changing how U.S. income tax is assessed on multinational corporations. The U.S. Department of Treasury has issued and will continue to issue regulations and interpretive guidance that may significantly impact how we will apply the law and impact our results of operations.

In addition, the Organization for Economic Cooperation and Development (OECD) has published proposals covering a number of issues, including country-by-country reporting, permanent establishment rules, transfer pricing rules, tax treaties and taxation of the digital economy. A significant majority of countries in the OECD's Inclusive Framework have agreed in principle to a proposed solution to address the tax challenges arising from the digitalization of the economy. Future tax reform resulting from this developmentthese developments may result in changes to long-standing tax principles, which could adversely affect our effective tax rate or result in higher cash tax liabilities. In 2018,Nearly 140 countries have signed up or agreed to sign up on a plan that would be implemented in 2023, setting a 15% minimum tax rate on corporations and a plan to reallocate part of the profits from the largest and most profitable businesses to countries where they make sales. The OECD's proposed solution envisages new international tax rules and the removal of all Digital Services Taxes (DST). The European Union has also published its proposal for a directive aimed at implementing the OECD rules on a 15% minimum effective tax rate in the European Commission proposed a series of measures aimed at ensuring a fair and efficient taxation of digital businesses operating within the European Union. SomeUnion Member States. Notwithstanding this, some countries, in the European Union and beyond, have unilaterally movedcontinue to introduce their own digital services taxoperate a DST regime to capture tax revenue on digital services more immediately. Notably France, Italy, Austria, the United Kingdom, Turkey, India, Spain and Kenya have enacted or will soon enact a digital tax. SuchOverall, future tax laws may increase our tax obligations in those countries or change the manner in which we operate our business.

In February 2022, we announced that our board of directors authorized the repurchase of up to $4.0 billion of our common stock, replacing our previously authorized $2.0 billion program from 2020, Altera Corp. filed a petition to appeal the decision with the Supreme Courtof which approximately $819 million remained. As part of the United States. On June 22, 2020,new program, we entered into a $2.0 billion accelerated share repurchase on February 10, 2022 and may repurchase the Supreme Court deniedremaining $2.0 billion over time.

The existence of these share repurchase programs could cause our stock price to be higher than it otherwise would be and could potentially reduce the petition. Inmarket liquidity for our stock. Although these programs are intended to enhance long-term stockholder value, there is no assurance they will do so because the fourth quartermarket price of 2020, we filed our 2019 U.S. Federal and state tax returns and included certain adjustments related to Altera forcommon stock may decline below the levels at which we previously recognized a reserve. As a result,repurchased shares and short-term stock price fluctuations could reduce the effectiveness of the programs.

Repurchasing our unrecognized tax benefits decreased by $96.9 million incommon stock will reduce the fourth quarteramount of 2020 with no impact on our effective tax rate.cash we have available to fund working capital, capital expenditures, strategic acquisitions or business opportunities, and other general corporate requirements, and we may fail to realize the anticipated long-term stockholder value of these share repurchase programs.

As of December 31, 2020,2021, we had U.S. federal net operating loss carryforwards of $2.19 billion and state net operating loss carryforwards of $1.28 billion. As of December 31, 2020,$2.39 billion and $1.36 billion, respectively, and we had U.S. federal and state research and development credit carryforwards of $398.4$494.8 million and $297.1$349.4 million, respectively. A portion of the U.S. net operating loss carryforwards and tax credit carryforwards could be subject to ownership change limitations governed by Section 382 or 383 of the Internal Revenue Code.Code and similar provisions of state law, or other limitations imposed under state law. Any such limitations on the ability to use our net operating loss carryforwards and other tax assets could adversely impact our business, financial condition and operating results.

Under GAAP, we review our intangible assets for impairment when events or changes in circumstances indicate the carrying value may not be recoverable. Goodwill is required to be tested for impairment at least annually. An adverse change in market conditions or financial results, particularly if such change has the effect of changing one of our critical assumptions or estimates, could result in a change to the estimation of fair value that could result in an impairment charge to our goodwill or intangible assets. Any such material charges may have a material and adverse impact on our operating results.

Our amended and restated certificate of incorporation, amended and restated bylaws and Delaware law contain provisions which could have the effect of rendering more difficult, delaying, or preventing an acquisition deemed undesirable by our board of directors. Among other things, our amended and restated certificate of incorporation and amended and restated bylaws include provisions:

These provisions, alone or together, could delay or prevent hostile takeovers and changes in control or changes in our management.management, and amendment of our amended and restated certificate of incorporation to change or modify certain of these provisions requires approval of a super-majority of our stockholders, which we may not be able to obtain.

As a Delaware corporation, we are also subject to provisions of Delaware law, including Section 203 of the Delaware General Corporation law, which prevents certain stockholders holding more than 15% of our outstanding common stock from engaging in certain business combinations without approval of the holders of at least two-thirds of our outstanding common stock not held by such 15% or greater stockholder.

Any provision of our amended and restated certificate of incorporation, amended and restated bylaws or Delaware law that has the effect of delaying, preventing or deterring a change in control could limit the opportunity for our stockholders to receive a premium for their shares of our common stock, and could also affect the price that some investors are willing to pay for our common stock.

The market price of our common stock has been and may continue to be highly volatile in response to various factors, some of which are beyond our control. In addition to the factors discussed in this “Risk Factors” section and elsewhere in this Annual Report on Form 10-K,report, factors that could cause fluctuations in the market price of our common stock include the following:

In addition, in the past, following periods of volatility in the overall market and the market price of a particular company’s securities, securities class action litigation has often been instituted against these companies. Any securities litigation can result in substantial costs and a diversion of our management’s attention and resources. We are currently subject to securities litigation and in September 2021, we entered into a binding agreement to settle a shareholder class action lawsuit. The proposed settlement resolves all claims asserted against us and the other named defendants in the shareholder class action lawsuit without any liability or wrongdoing attributed to them personally or to us. Under the terms of the proposed settlement, we paid $809.5 million from cash on hand in the fourth quarter of 2021. The settlement agreement is subject to final approval by the U.S. District Court for the Northern District of California. We may experience more such litigation following any future periods of volatility.

Concurrent with the issuance of the 20212024 Notes and 20242026 Notes we entered into note hedge transactions with certain financial institutions, which we refer to as the option counterparties. The note hedge transactions are generally expected to reduce the potential dilution upon any conversion of the 20212024 Notes and 20242026 Notes and/or offset any cash payments we are required to make in excess of the principal amount converted with respect to the 20212024 Notes or 20242026 Notes as the case may be. We also entered into warrant transactions with the option counterparties. However, the warrant transactions could separately have a dilutive effect to the extent that the market price of our common stock exceeds the applicable strike price of the warrants.

The option counterparties or their respective affiliates may modify their initial hedge positions by entering into or unwinding various derivatives contracts with respect to our common stock and/or purchasing or selling our common stock or other securities of ours in secondary market transactions prior to the maturity of the 20212024 Notes and 20242026 Notes, as applicable (and are likely to do so during any applicable observation period related to a conversion of the 20212024 Notes and 20242026 Notes as applicable, or following any repurchase of the 20212024 Notes and 20242026 Notes, as applicable, by us on any fundamental change repurchase date or otherwise). This activity could cause or avoid an increase or a decrease in the market price of our common stock.

In addition, if any such convertibleAdditionally, we entered into similar note hedge transactions and warrant transactions failin connection with the issuance of our 2021 Notes which matured on September 15, 2021. The note hedge transactions entered into in connection with the 2021 Notes expired on September 15, 2021 and the warrant transactions in connection with the 2021 Notes expire over a 60 trading day settlement period commencing 90 days after the maturity of the 2021 Notes and scheduled to become effective,end on March 11, 2022. These warrant transactions could also have a dilutive effect to the option counterparties or their respective affiliates may unwind their hedge positions with respect toextent that the market price of our common stock which could adversely affectexceeds the valuestrike price of our common stock.such warrants.

We are currently involved in, and may in the future be involved in, legal proceedings, claims, investigations, and government inquiries and investigations arising in the ordinary course of business. These proceedings, which include both individual and class action litigation and administrative proceedings, have included, but are not limited to matters involving content on the platform or our actions related thereto, intellectual property, privacy, data protection, cybersecurity, consumer protection, securities, employment and contractual rights. Legal risk may be enhanced in jurisdictions outside the United States where our protection from liability for content published on our platform by third parties may be unclear and where we may be less protected under local laws than we are in the United States. Future litigation may be necessary, among other things, to defend ourselves, and the people on Twitter or to establish our rights. For information regarding legal proceedings in which we are involved, see “Legal Proceedings” in Note 16 of the Notes to Consolidated Financial Statements included in Part II, Item 8 of this Annual Report on Form 10-K, which is incorporated herein by reference.

Total revenue was $3.72$5.08 billion, an increase of 7%37%, compared to 2019.2020.

Net loss was $221.4 million in 2021, compared to net loss of $1.14 billion in 2020, which was inclusive of a $1.10 billion provision for income taxes related to the establishment of a valuation allowance against deferred tax assets. Net income was $1.47 billion in 2019, which was inclusive of a $1.21 billion benefit from income taxes related to the establishment of deferred tax assets from the intra-entity transfer of intangible assets.

Cash, cash equivalents and short-term investments in marketable securities totaled $7.47$6.39 billion as of December 31, 2020.

In 2021, we continued to make progress on our brand and direct response offerings, with updated ad formats, improved targeting, and better measurement. Our strategy is designed to help advertisers achieve their goals at every stage of the marketing funnel -- from awareness and consideration, all the way through to conversion. We are focused on improving both our suite of performance ad products and improving our tools to drive awareness and consideration.

The COVID-19 pandemic has resulted in public health responses including travel bans, restrictions, social distancing requirements,had, and shelter-in-place orders, whichcontinues to have, a significant impact around the world and has impacted our business, operations, and financial performance in different ways. Following the start of the pandemic, we saw increased use of Twitter as people sought to stay informed and connect with others, and in the fourth quarter of 2020, our year-over-year growth in mDAU remained strong, driven by global conversations related to current events and ongoing product improvements. Our work to serve the public conversation, by helping people find trusted sources of information, and better organizing and surfacing the many topics and interests that bring people to Twitter, helped us retain new and recently reactivated accounts in 2020. We also continue to benefit from the ongoing impact of product improvements, including continued increases in relevance across notifications, search, Explore, and the Home timeline.

In the three months ended December 31, 2020,2021, ad engagements increased 35%decreased 12% from the three months ended December 31, 2019,2020, driven by strong growth ina mix shift toward lower funnel ad impressions due to our growing audienceformats and increased demand for ads.15-second video views, which, although they have higher cost per ad engagement, generally have lower engagement rates. In the three months ended December 31, 2020,2021, cost per ad engagement decreasedincreased by 3%39% compared to the three months ended December 31, 2019, which was largely2020, primarily driven by like-for-like price increases across most ad formats due to the impact of COVID last year, as well as a functionmix shift toward lower funnel ad formats and 15-second video views.

In 2020,2021, data licensing and other revenue increased by $43.0$62.8 million or 9%12% compared to 2019.2020. The increase was attributable to expanded partnershipsgrowth in MoPub and to Twitter Development Platform (formerly known as Developer and Enterprise Solutions (DES),Solutions) revenue attributed to contract renewals with higher fees. In December 2021, we completed the wind down of MoPub Acquire (formerly known as CrossInstall) and on January 1, 2022, we closed the sale of MoPub. MoPub and MoPub Acquire generated approximately $217.9 million in revenue in 2021, the significant majority of which was reflected in "Data Licensing and Other" revenue.

In March 2020, our Board of Directors authorized a program to repurchase up to $2.0 billion of our common stock over time. Repurchases may be made from time to time through open market purchases or through privately negotiated transactions subject to market conditions, applicable legal requirements and other relevant factors. The repurchase program does not obligate us to acquire any particular amount of our common stock and may be suspended at any time at our discretion. In the year ended December 31, 2020,2021, we repurchased 5.716.9 million shares for an aggregate amount of $250.6 million, including 98,000$930.5 million. The repurchases include 120,000 shares for $5.3 million that were not settled as of December 31, 20202021 that are presented as treasury stock on the consolidated balance sheets under the program.as of such date.

As of December 31, 2020,2021, we had $7.47$6.39 billion of cash, cash equivalents and short-term investments in marketable securities, of which $255.1$279.6 million was held by our foreign subsidiaries. We do not plan to indefinitely reinvest these funds held by our foreign subsidiaries and have accrued the incremental taxes due as part of repatriation. In October 2021 we paid the $809.5 million settlement related to the shareholder class action lawsuit discussed in Note 16 – Commitments and Contingencies.

We believe that our existing cash, cash equivalents and short-term investment balances, and our credit facility, together with cash generated from operations and continued access to capital markets, will be sufficient to meet our working capital, and capital expenditure, and other cash requirements for at leastincluding authorized share repurchases over the next 12 months and beyond. From time to repaytime, we may need or choose to seek additional financing through the $954.0 million principal associated withissuance of equity, equity-linked or debt securities to operate or grow our 2021 Notes due in September 2021, despitebusiness. Our ability to obtain additional financing, if and when required, will depend on investor and lender demand, our operating performance, the uncertainty related tocondition of the COVID-19 pandemic.capital markets, and other factors.

We have a revolving credit agreement with certain lenders which provides for a $500.0 million revolving unsecured credit facility maturing on August 7, 2023. We are obligated to pay interest on loans under the credit facility and other customary fees for a credit facility of this size and type, including an upfront fee and an unused commitment fee. The interest rate for the credit facility is determined based on calculations using certain market rates as set forth in the credit agreement. In addition, the credit facility contains restrictions on payments including cash payments of dividends. In March 2021, we entered into an amendment to the revolving credit agreement to increase the amount of indebtedness we may incur from $4.5 billion to $6.0 billion and to permit the convertible note issuance and hedge transactions associated with the 2026 Notes. In February 2022, we amended our existing revolving credit agreement to permit our repurchases of our common stock in an aggregate amount not to exceed $4.0 billion. As of December 31, 2020,2021, no amounts had been drawn under the credit facility.

We have concluded that our data licensing arrangements, which grant customers a right to our intellectual property (IP) for a defined period of time, may contain a single performance obligation satisfied at a point in time (Historical IP) or over time (Future IP), or may contain two or more performance obligations satisfied separately at a point in time (Historical IP) and over time (Future IP). In some of our data licensing arrangements, pricing is a fixed monthly fee over a specified term. In arrangements with a single performance obligation satisfied over time, data licensing revenue is recognized on a straight-line basis over the period in which we provide data as the customer consumes and benefits from the continuous data available on an ongoing basis. In arrangements with at least two performance obligations, we allocate revenue on a relative basis between the performance obligations based on standalone selling price (SSP) and recognize revenue as the performance obligations are satisfied.

Other revenue is primarily generated from service fees from transactions completed on our mobile ad exchange. Our mobile ad exchange enables buyers and sellers to purchase and sell advertising inventory by matching them in the exchange. We have determined we are not the principal in the purchase and sale of advertising inventory in transactions between third-party buyers and sellers on the exchange because we do not obtain control of the advertising inventory. We report revenue related to our ad exchange services on a net basis for the fees paid by buyers, net of costs related to acquiring the advertising inventory paid to sellers.

We recognize tax benefits from uncertain tax positions if we believe that it is more likely than not that the tax position will be sustained upon examination by the taxing authorities based on the technical merits of the position. Although we believe we have adequately reserved for our uncertain tax positions (including net interest and penalties), we can provide no assurance that the final tax outcome of these matters will not be different. We make adjustments to these reserves in accordance with income tax accounting guidance when facts and circumstances change, such as the closing of a tax audit. To the extent that the final tax outcome of these matters is different from the amounts recorded, such differences may impact the provision (benefit) for income taxes in the period in which such determination is made. We record interest and penalties related to our uncertain tax positions in our provision (benefit) for income taxes.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

The critical audit matter communicated below is a matter arising from the current period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that (i) relates to accounts or disclosures that are material to the consolidated financial statements and (ii) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

As described in Notes 21 and 32 to the consolidated financial statements, the Company generated $3.2$4.5 billion of its revenue from the sale of advertising services, with $0.5$0.6 billion from data licensing and other arrangements, for the year ended December 31, 2020.2021. Significant judgments made by management are (i) identifying the performance obligations in the contract, (ii) determining the basis for allocating contract consideration to performance obligations, (iii) determining whether the Company is the principal or the agent in arrangements where another party is involved in providing specified services to a customer, and (iv) estimating the transaction price to be allocated for contracts with tiered rebate provisions.

The principal considerations for our determination that performing procedures relating to revenue recognition, specifically related to the identification of performance obligations, is a critical audit matter are the significant amount of judgment by management in identifying performance obligations. This in turn resulted in significant audit effort and a high degree of subjectivity in performing procedures and evaluating audit evidence.

Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to the revenue recognition process, including controls over the identification of performance obligations. These procedures also included, among others, examining revenue arrangements on a test basis and testing management’s process for (i) determining whether the criteria for revenue recognition have been met based on the terms and performance under the arrangement, and (ii) identifying performance obligations and, where applicable, determining whether the Company is the principal or agent for the performance obligation identified.