if you click "share" on a youtube video, the link usually looks like this: https://youtu.be/XfELJU1mRMg?si=OPxJpFpPaZN10Bor, note that there is "?si=" in there, everything after that is a tag with your persona and timestamp, so if you click that link on any other messenger / site, encrypted or not, google instantly knows that i sent you this video. however the link works just the same if you remove everthing from "?si=" onwards -> "https://youtu.be/XfELJU1mRMg"