Nostr
Notes and Other Stuff Transmitted by Relays — a decentralized social protocol based on cryptographic keys instead of accounts. Created in 2020 by the pseudonym "fiatjaf". Popular in Bitcoin circles; Jack Dorsey funded its development.
Model: your identity = a keypair (npub public, nsec private). Posts are signed and sent to "relays" (servers). No accounts, no central servers — switch relays freely, your identity follows. Distinct from ActivityPub: simpler, no server identity, censorship-resistant (publish to any relay). Zaps: Bitcoin Lightning micropayments built in. Clients: Damus (iOS), Amethyst (Android), Primal. Criticism: relay spam, hard NSFW moderation, small outside the crypto bubble. A distinct philosophy from Bluesky/Mastodon.