Metastream allows you to watch internet videos with friends. It synchronizes media on websites so you can watch together.
StreamParty is a community, that allows you to watch video streams in sync with your friends all across the world, on multiple services, right on their website.
OpenTogetherTube lets you watch videos with your friends as easily as possible. It's completely open source, and able to be easily self-hosted via provided docker images.
Watch2Gether lets groups of users watch videos in-sync together. At the same time users can communicate through a build-in chat-room and use web cam and audio chat. Available media sources are Youtube, Vimeo, Dailymotion and Soundcloud.
Watch2Gether vs Rave opinions
Great app when your friends are far or when you're quarantined at home!
Enjoy movie night online with your long-distance partner, start a watch party with good buddies, or hang out and binge anime with your best friend. Hyperbeam helps you stay close, even when you’re apart.
Kosmi is a free real time application and communication platform that offers voice, text and video calls along with games and applications such as SNES Party, NES Party, OpenArena, Poker, Virtual Cardtables, Synced YouTube and Cowatch Video.
Syncplay program allows you and your friend/partner/family member to watch same video file simultaniously on different PCs and different location by syncing playback of MPC-HC, mpv, mplayer2 and VLC players.
Netflix Party is a Chrome extension for watching Netflix remotely with friends, e.g., for movie nights with that long-distance special someone. It synchronizes video playback and adds group chat.
Teleparty vs Rave opinions
CyTube vs Rave opinions
Free and open source alternative to Rave and Watch2Gether, what else?