In my experience, first generation happened on BBSs (contemporaneous with usenet, which wasn't on my radar until it was nearly dead). Then came niche community discussion boards and AOL. Then, Geocities and webrings. Friendster came out a few months earlier than MySpace, but they were close enough to be the same generation. By my count, TikTok is sixth generation? I can't help but feel that I'm missing a few; not even considering my anglocentric experience.