Facebook has told ad agencies that it is getting ready to test mid-roll ads in its videos. Facebook users will soon encounter the new mid-roll ad format in clips from select publishers, with ads interrupting their regular video viewing at the 20-second mark.

Recode was first to report the news Monday; Marketingland.com later added that the new mid-roll ads will be limited to 15 seconds or less. Clips need to be at least 90 seconds long to qualify for a mid-roll ad break.

Facebook reportedly told publishers that they will get 55 percent of the mid-roll ad revenue generated with their videos. The site doesn’t offer any pre-roll ads, but has given publishers a cut of ad revenue generated with ads that play between videos. The company also started testing mid-roll ads in live video last summer.

Facebook says that its users watch 100 million hours of video every day. The company has invested heavily into growing video views; it is paying select publishers to use its live streaming service, and recent tweaks in Facebook’s apps are meant to simplify video discovery.