YouTube’s testing a new way to react to certain elements of video clips with ‘Timed Reactions’, which are essentially emoji reactions that you can add to a specific frame in the playback.
As you can see in this example, similar to YouTube’s Timed Comments, Timed Reactions will enable users to attach an emoji character that captures their response to certain elements of a clip.
As explained by YouTube:
“For viewers in the experiment you’ll tap comments, and you’ll see a popup tab in the bottom right hand corner of a video on mobile. Tap it, to see a set of reactions that you can then use to react to specific moments of the video you’re watching.”