Streaming-TV platform Roku(ROKU -6.60%) reported fourth-quarter earnings results on Thursday, and investors were clearly impressed. The company's core operating metrics continued to march in the right direction, while the advertising business is putting up strong growth. Some of that was already known, as Roku had disclosed preliminary estimates on active accounts and hours streamed in early January.

Thanks to executing well on numerous fronts, Roku now expects to hit $1 billion in revenue in 2019.

Check out the latest Roku earnings call transcript. 

TV episodes on a Roku TV

Image source: Roku.

Growing the audience while strengthening monetization

Total revenue in the fourth quarter jumped 46%, to $275.7 million, exceeding the high end of the company's own guidance for $265 million. Within that top line, highly profitable platform revenue soared nearly 80%, to $151.4 million. That segment continues to represent the vast majority of Roku's overall gross profits -- 97%, to be precise, in the fourth quarter. Player unit volumes increased 30%, while average selling prices (ASPs) fell 8%, as affordable players (under $50) continue to be popular sellers.

Active accounts have grown to 27.1 million, and Roku streamed 7.3 billion hours of content during the quarter. Average revenue per user (ARPU), which is calculated as trailing-12-month (TTM) platform revenue divided by active accounts, increased to $17.95. The platform segment is predominantly advertising, so Roku's ad business is performing extremely well. The company says video ad impressions more than doubled in 2018.

In other words, Roku continues to grow its audience (active accounts growth) while strengthening monetization of that audience (ARPU gains). That's a potent combination driving the business forward. Roku said last month that it's getting into premium subscriptions, selling access to popular channels like CBS' Showtime and Lionsgate's Starz, among others, while getting a cut of those sales. That move has the potential to build on the platform segment's ongoing momentum.

Adjusted EBITDA soared 70%, to $24.5 million, and non-GAAP net income came in at $0.05.

Hitting $1 billion

Roku's guidance came in above expectations, as well. The company expects total revenue in 2019 to exceed $1 billion for the first time ever, up from $742.5 million in 2018. That's slightly ahead of the $985.2 million in sales that the Street was expecting this year.

Platform revenue is expected to represent approximately two-thirds of sales, and gross profit should jump to a range of $445 million to $450 million. Roku, however, still expects to lose $80 million to $90 million.

For just the first quarter, revenue is forecast at $185 million to $190 million, mostly comparable to current expectations of $188 million. Gross profit this quarter should be $86 million to $90 million, with a net loss of $28 million to $32 million.