ActivityPub
The open standard that lets independent social servers exchange posts, follows and replies — the protocol underpinning Mastodon and Threads federation.
ActivityPub is the open W3C standard that lets independent social servers send each other posts, follows, likes and replies in a common format. It's the protocol behind Mastodon and the federation features Threads has been switching on.
Think of it as email for social: your server speaks the same language as everyone else's, so the fediverse holds together without a central owner. For founders it's the reason microblogging on these platforms isn't trapped in one app — your followers can live anywhere that speaks the protocol.
See also