The popular online video streaming site is testing ads that appear before or after shows, according to Motherboard. The ads, which vary in length, have only promoted Netflix’s original programming.

The Netflix test has been going on for at least a week, according to Cord Cutters News, which first reported the ads. The company confirmed the limited ad run to Motherboard, adding in a statement: “As with any Netflix product test, this may never come to all our members.”

If Netflix (NFLX) decides to fully roll out ads for its own programs, then the company would be following a similar ad model used by HBO, which shows ads for its own series and films both on TV and through the cable network’s online streaming platforms.

Of course, one of the reasons Netflix has been able to grow its huge global subscriber base (60 million users and climbing) is because so many customers are willing to pay for ad-free content. But the company could be leaving a lot of money on the table by doing without commercials, especially from third parties. So far, the commercials have been tested in a limited number of markets with a fraction of the service’s subscribers. Motherboard’s Jason Koebler adds:

It’s worth noting that, though Netflix hasn’t had any ads so far, it has the potential to deliver much more targeted ads (which can be sold for higher rates) than a standard cable company. Netflix has a detailed history of every show you’ve ever watched, meaning it can infer your interests and so on.

Netflix CEO Reed Hastings denied in a Facebook post that Netflix would broadcast commercials from outside companies. Instead, he said the ads would be limited to trailers for Netflix-produced shows.

“No advertising coming onto Netflix. Period,” Hastings said. “Just adding relevant cool trailers for other Netflix content you are likely to love.”

(The original story was updated with comment from Netflix CEO Reed Hastings)