Since the end of June, YouTube has been slowly rolling out GIF-like video thumbnails that play three seconds of the video. As of this writing, many already have this feature on their YouTube pages, although it has been available to a select few as early as February.
According to YouTube, the platform has been letting a growing percentage of its user base see these previews on their YouTube homepages, search results, watch page, subscriptions tab, and trending tab. The previews show up only on Chrome versions 32 and up and Opera version 19 and up; they don’t work on mobile devices.
Videos have to be longer than 30 seconds to be eligible for an animated thumbnail, but YouTube also uses criteria like video topic and content to decide whether to show a preview or not. Currently, if you don’t see a preview for a new video within two days, it means it’s not eligible, although videos from years ago are still getting them. Live videos don’t seem eligible either.
The moving thumbnails are automatically generated with AI from a clip from the first half of the video that “it believes gives the best idea of what your video is about,” without any input from the video creators. For now, video creators are not able to choose what preview is shown, which seems like a loss of creative control, seeing as they can customize their still image thumbnails.