Shares of Roku (NASDAQ:ROKU) are surging in after-hours trading on Wednesday, following the company's first-quarter earnings release. The stock is up nearly 9% as of 4:45 p.m. EDT. The stock's rise comes after Roku reported first-quarter results that crushed expectations, featuring revenue growth that accelerated during the quarter.

The company's growth continues to be driven by soaring platform revenue, which is benefiting from higher engagement, new accounts, and a more than doubling of video ad impressions compared to the year-ago quarter.

The Roku Channel displayed on a TV

Roku Channel. Image source: Roku.

Wild momentum

Roku's revenue surged 51% year over year to $206.7 million in the company's first quarter of 2019, easily beating analysts' consensus estimate for revenue of $192 million. This is a meaningful acceleration from Roku's 46% revenue growth in its fourth quarter of 2018. The primary driver for this growth was a 79% increase in platform revenue (an acceleration from 77% growth in Q4), which accounted for 65% of total revenue during the period.

Helped by a 76% year-over-year increase in platform gross profit dollars, the company's loss per share of $0.09 was better than analysts' average forecast for a loss per share of $0.24. Roku's loss per share was $0.02 worse than it was in the year-ago quarter, though,because the company is investing heavily in its future by ramping up its spending on research and development, sales and marketing, and general and administrative operating expenses.

The number of active accounts notably increased 40% year over year to 29.1 million, and streaming hours soared 74% over the same timeframe to 8.9 billion.

Multiple drivers

The quarter highlighted the diversified drivers for Roku's platform revenue. Broad-based strength in the company's share of third-party subscription video on demand and transactional video on demand revenue, as well as growth in audience development revenue and video advertising sales, were all key drivers for platform revenue, management explained in its first-quarter shareholder letter. The company also said its "monetized video ad impressions across the platform more than doubled, and we expect that trend to continue throughout 2019."

Roku management is optimistic about how it has positioned itself amid the ongoing shift away from linear TV to internet-based direct-to-consumer models.

"As the TV streaming market evolves, we see subscription-based and ad-supported business models co-existing and attracting substantial consumer audiences, with revenue participation for Roku in both models," the company said in its quarterly shareholder letter. "We believe the expanding roster of direct-to-consumer services makes the Roku platform even more appealing to consumers seeking increased content choice and control."

Whether content is offered with ads, through subscriptions, or on a transactional basis, Roku's platform is benefiting from an evolving TV landscape.