Watch YouTube together, in sync
Open the same video, join the same room: play, pause and seeking stay in sync, and the next video you pick opens for the others.
Ads, handled
When YouTube shows an ad to one of you, the room pauses at the same moment for everyone, then starts again together when the ad is over.
Playlists and the next video
The video and its playlist are shared with the room. When one of you picks another video, the others are taken to it. Shorts are not supported.
Questions
Do we need a YouTube account?
No, unless the video asks for one. Futari needs no account either.
Does it work on YouTube Music?
No, only on youtube.com.