But below the big three, some new companies are quickly climbing the ranks, according to research by market tracker Parks Associates.

The fourth-largest Internet video service ranked by number of subscribers is Major League Baseball’s MLB.TV, followed by premium cable channel spinoffs HBO Now and Starz. CBS’s (CBS) Showtime’s Internet service ranked eighth and CBS All Access, the home of the latest Star Trek TV series, was ninth.

Rapid growth has been fueled by interest both from cord cutters, who have dropped traditional cable TV subscriptions, as well as more omnivorous households that subscribe to both cable and Internet-only “over-the-top” services, as the industry calls them. One-third of all households with a broadband Internet service subscribe to at least two “over-the-top,” or OTT, services, Parks said.

“While the top three are no surprise, the big story over the past year has been the rapid subscriber growth for OTT video services from HBO, Showtime, and Starz,” Brett Sappington, senior director of research at Parks, says. “The combination of recognized brands and popular original content is driving demand for their offerings.”

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Rounding out the top 10 were two very different takes on video entertainment. Google’s (GOOGL) two-year-old YouTube Red service, which lets subscribers watch YouTube videos without ads and gain access to some special premium shows, ranked seventh overall. And Dish Network’s (DISH) Sling TV, which offers a more traditional bundle of cable TV channels over the Internet, was 10th.

Parks said it is tracking more 200 different Internet video services in total, ranging from giants like Netflix (NFLX) and Amazon (AMZN) to tiny players like horror-focused Shudder and video gamer-oriented Rooster Teeth. While many include advertising, nine out 10 offer some type of premium subscription as well, Parks said.