Fediverse
Also known as: activitypub, mastodon
A network of interconnected social platforms (Mastodon, Pixelfed, Bluesky-ATProto) built on open protocols.
Fediverse services speak protocols like ActivityPub so accounts on different servers can follow, reply and share across the whole network. There's no single owner, no unified ad auction and no cross-platform behavioural profile of you being sold.
Privacy still depends on the individual server you choose (its logging, its moderation, its funding), but the architecture removes the incentive for surveillance advertising that dominates centralised social media.