Thanks, Anthony. We executed well in the first quarter and delivered particularly strong results.
Before taking your questions, I will walk through operational and financial highlights and address our outlook. Strong Roku TV demand and continued strength in player sales delivered an incremental 2 million active accounts in the first quarter to 29.1 million active accounts.
Our scale and per user engagement drove 1.6 billion incremental streaming hours sequentially to 8.9 billion hours in the quarter. Roku users streamed more content on our platform in the last 6 months than they did in all of 2017. ARPU increased another $1.11 sequentially to $19.06 driven by broad-based growth in content distribution, monetized video ad impressions and audience development spend by our content partners. Total Q1 revenue increased 51% year-over-year to $206.7 million with Platform revenue up 79% to $134.2 million to a record 65% of total revenue. Player revenue growth of 18% year-over-year again came in ahead of expectations driven by strong core retail channel sales growth. Player units were up 21% year-over-year and ASPs were down 4% as we continue to see strong demand for sub $50 players.
Our key financial performance metric is gross profit, which was up 60% year-over-year this quarter to $100.9 million marking our second consecutive quarter above $100 million despite this being our seasonally lowest quarter. Gross margin was 48.8%, up 260 basis points year-over-year with continued mix shift to the higher margin Platform business partially offset by declining player margins that helped drive rapid unit and active account growth. OpEx in the quarter grew 59% to $111.6 million driven by 33% growth in headcount and higher stock-based compensation.
Excluding stock-based comp, OpEx was up 43% year-over-year, which was below our revenue and gross profit growth. OpEx came in below expectations primarily due to the timing of new hires coming in later than planned, which when combined with gross profit upside delivered positive adjusted EBITDA of $10 million in Q1. With that, let’s turn over to our outlook for the full year. Based on strong Q1 results and momentum into Q2, we are raising our 2019 outlook to $1.04 billion in revenue and $470 million in gross profit at the midpoint up 40% and 41% year-over-year respectively compared to roughly 36% year-over-year in our prior outlook. Included in our outlook Platform revenue mix is expected to be roughly two-thirds of total revenue, up from 56% in 2018.
For modeling purposes, you should continue to model full year Platform gross margin in the low 60s as a percent of revenue driven by continued mix shift to video advertising and the introduction of premium subscriptions.
For players, we expect player gross margin to be in the low single-digits in 2019. We remind you that we are not optimizing for player gross profit as our strategy of trading player margin for account growth and platform revenue growth continues to work well. We plan to manage the business to roughly EBITDA breakeven in 2019, so some of the Q1 upside is expected to flow through to the full year. Stock comp of roughly $75 million and depreciation and amortization and net other income of $10 million, are reflected in our outlook for roughly $70 million of net income loss in 2019.
For Q2, our outlook is for year-over-year revenue growth up 42% at the midpoint with Platform revenue representing roughly two-thirds of total revenue.
Continued mix shift to video advertising is expected to remain a drag on Platform gross margins and when combined with mid single-digit player gross margin, our combined outlook for Q2 is for roughly 45% gross margins.
As a reminder in Q2 of 2018, player gross profit benefited from a release of accruals of $8.9 million related to potential IP licensing liabilities that did not materialize and are not expected to be realized.
Excluding these accrual releases in Q2 of 2018, gross margin would have been 44% versus 50% as reported. Q2 OpEx is expected to be roughly 15% higher than in Q1 as we recognized the full quarter impact of the hiring that took place in Q1 and new hires in Q2.
We also recently signed a new lease agreement that was not in our prior outlook and adds an incremental $2 million to $3 million per quarter.
As a result, we expect to report an adjusted EBITDA loss of roughly $7.5 million at the midpoint and a net income loss of roughly $27.5 million which includes stock-based comp of $18 million and $2 million of depreciation and amortization and net other income in the quarter. We ended the quarter with $290 million of cash equivalents and short-term investments, which included net proceeds of $98 million from the sale of Class A common stock. Subsequent to the quarter end, we upsized our credit facility by $50 million to $200 million consisting of $100 million revolver and $100 million of available term debt, but neither has been drawn. I will summarize by saying how pleased we are with the performance of the business and the strong momentum we are seeing across the broader streaming landscape that benefits Roku. With that, let’s turn over the call for questions. Operator?