Fediverse glossary: Mastodon, Bluesky, Nostr and the open social web explained
ActivityPub, instances, federation, AT Protocol, relays — the terms you need before your organisation posts on open social networks.
Open social networks are where many communities moved when they wanted platforms no single company controls. The vocabulary can be off-putting. Here are the terms that matter, in plain language.
The core terms
- FediverseThe family of independent servers that talk to each other with the same protocol, so a user on one can follow a user on another.
- ActivityPubThe open standard the fediverse speaks. Mastodon, Pixelfed and Lemmy all use it.
- Instance (server)One independently run server, such as mastodon.social. Your address includes it: @name@server.
- FederationServers exchanging posts with each other. Your followers can be on many different servers.
The networks, in one line each
- Mastodon — short posts, like X, spread across thousands of servers.
- Pixelfed — photo sharing, like Instagram, on the fediverse.
- Lemmy — communities and threaded discussion, like Reddit.
- Bluesky — short posts on the AT Protocol, a different open protocol with its own way of moving accounts between providers.
- Nostr — posts signed with your own key and sent to relays, with no account on any server.
Other terms you'll meet
- AT Protocol — the protocol behind Bluesky.
- Handle — your public name, e.g. @name@mastodon.social on Mastodon or name.bsky.social on Bluesky.
- Relay — on Nostr, a server that stores and passes on posts. You usually publish to several.
- Key pair — on Nostr, your identity: a public key others follow and a secret key that signs your posts. Keep the secret key safe.
- Access token / app password — a credential you create so a tool can post for you without your real password.
- Community — on Lemmy, a topic forum that posts are submitted to.
How does an organisation post to all of them?
- 1Choose your accounts
Pick a server for each fediverse network (or run your own), and a Bluesky and Nostr identity.
- 2Connect them once
Each connects differently: Mastodon with an access token from your server, Pixelfed by signing in on your server, Lemmy with your account, Bluesky with an app password, Nostr with a remote signer or key.
- 3Publish together
Write once and publish to the open networks alongside Facebook, Instagram and the rest — each checked against its own limits.
Is Bluesky part of the fediverse?
Not strictly. The fediverse usually means ActivityPub networks like Mastodon. Bluesky uses the AT Protocol, though bridges between the two exist.
Do I need my own server?
No. You can join an existing server. Larger organisations sometimes run their own so their address carries their domain.
Is Nostr a server?
No. Nostr has no accounts on servers — you hold a key and publish signed posts to relays.