Facebook will start inserting video advertisements into its users' feeds from this week. The videos will play automatically as they appear on any given page, on both the web and smartphones. The first ad is a teaser trailer for the March release of Divergent. The trailer was produced specifically for Facebook users, and if earlier rumors were true, should be around 15 seconds in length. The company calls it a test that will only be seen by "a small number of people," but it's clearly the first step in a larger rollout.

Facebook notes that, although the videos will automatically play, they'll be muted unless clicked or tapped by a user. After a video is finished, users will be given the option to replay it or choose from other clips from the same marketer. For mobile users, Facebook promises that videos will be downloaded in advance over Wi-Fi, so even if you're using mobile data when you first see the advertisement, it won't cost you anything in data fees.

Update: Following the Wall Street Journal's report this morning, Facebook has now officially launched video advertisements. This post has been updated to reflect that fact.