Roku (NASDAQ:ROKU) has been absolutely crushing it in recent quarters, and continues to guide 2019 revenue to over $1 billion. Total active accounts hit 29.1 million in the first quarter, and average revenue per user (ARPU) keeps marching steadily higher. Roku defines ARPU as trailing-12-month platform revenue divided by the average number of active accounts during that time, and the platform business is predominantly advertising.

The company is the largest streaming-TV platform in the U.S. -- and is extending its lead.

Roku platform displayed on a Roku TV

Roku TVs are an important source of active account growth. Image source: Roku.

Roku has the largest installed base in the U.S.

Roku doesn't disclose unit sales or provide a geographical breakdown of its user base, but it grabbed over 30% of connected TV device sales in the first quarter, according to recent estimates from Strategy Analytics. The market researcher now estimates that there are over 41 million Roku devices in use in the U.S., which includes its streaming-media players, as well as Roku TVs, smart TVs made by third-party manufacturers that integrate Roku's platform.

An active account may be accessed by multiple users and through multiple devices, which is how the estimated installed base can be greater than the number of active accounts. Roku's installed base now represents 15.2% of all media-streaming devices in the country, according to the report.

Trailing Roku is Amazon.com in No. 2 with 12% of U.S. sales in the first quarter, and Samsung's Tizen platform comes in at No. 3 with 11%. Alphabet's Google garnered 9% of sales with Android TV and Chromecast.

Chart showing devices in use for different streaming TV platforms

Image source: Strategy Analytics.

Roku has long billed itself as an agnostic platform, not trying to push any given video-streaming service over another. The company simply wants to provide as many choices as possible, and let consumers choose what to watch. That approach seems to be resonating with the market.

"Roku's extensive content offering, comprehensive search function and simple and intuitive user interface have been key factors in its success, alongside affordable hardware and regularly updated software," Strategy Analytics' David Watkins said in a statement. "Roku has managed to establish itself as a highly respected and trusted brand in the US with no perceived hidden agenda when it comes to promoting content on its platform."

However, Roku lacks international brand recognition compared to the larger tech behemoths that it competes with. That will make expanding abroad more challenging. "Revenue in international markets was less than 10% for all periods presented," Roku notes in regulatory filings.

Looking ahead, Strategy Analytics expects Roku's installed base to swell to over 52 million by the year's end, which would represent 18% of all connected media devices in the U.S.