It’s easy for a Netflix subscriber to watch one episode after another of a favorite show: A viewer makes a selection and lets them keep on coming. But now subscribers face a different interruption: promotional videos, which can last from 10 to 20 seconds. Almost like a commercial, they appear between episodes, reminding viewers not to miss a different show on Netflix.

Netflix users complained they could neither skip nor mute the videos. But Netflix said that  the company was not adding commercials but merely testing promotional videos, which can in fact be skipped.

“We have been looking at ways to insert rich video into our experiences for several years,” said Smita Saran, a company spokeswoman.“These video promos are actually personalized recommendations for titles we think a member may enjoy watching,” Ms. Saran said. “In this particular case, we are testing whether surfacing recommendations between episodes helps members discover stories they will enjoy faster.”It was not clear how many subscribers were seeing the videos. Ms. Saran said that the company does not comment on where such tests are conducted but that they are customarily done globally.

Netflix, which has over 100 million subscribers, reported last month that it signed up 674,000 new subscribers after forecasting that it would add 1.2 million. In the crowded market of streaming services, there’s an imperative for it to keep its subscribers from straying.Netflix runs hundreds of tests and some are incorporated into the service as features that subscribers can use, while others are invisible. For example, Netflix experimented with movie previews in which a trailer played after users hovered over a title. That became a permanent feature after being tested for years.

The promotional videos being tested have been in the works for several years. The tests have to be successful with customers worldwide before they become permanent. Netflix said that it was interested in hearing from customers about its experiments but that it would ultimately be “looking at their behavior within the service.”

For now, users can skip the promotional videos or watch them and be nudged toward a new series. Either way, Netflix will be making note.