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.