Users send each other urls in a peer to peer way, just like audio data (so no urls are sent to the server). The browser then navigates to the url received.
The browser itself is a Chromium Browser (the Electron BrowserView).
The website is built with Notion + Super.so.
Let me know if you have any questions :)
At first I tried to send the whole dom from one user to another, so users would see the exact same thing (no personalization like some sites do) -- and that didn't work out. It was easy to stream the html from one user to another via webrtc but the styles and javascript seemed non trivial.
So I landed at this more simple version. I haven't experimented much with browser extensions but for that approach, I would just create the peer connection between users in the extension. And simulate a click whenever a leader changes urls. (that may actually be better than this current Chromium browser version)