@ AT Protocol Glossary

The AT Protocol (short for Authenticated Transfer Protocol, or just atproto) is an open standard for building social apps that aren’t owned by any one company — the way email or the web aren’t owned by anyone.

The core idea is simple, and rests on three moving parts:

1. Your data lives in a signed “repository.” Every post, like and follow you make is a small record cryptographically signed by you. Because it’s signed, anyone can verify it’s genuinely yours without asking a central server for permission.
2. Your identity is permanent and portable. You get a stable ID (a DID) and a friendly username (a handle, which is just a domain name). You can move your whole account — data, followers and all — from one host to another and keep your identity. That’s the “credible exit” that stops lock-in.
3. Anyone can build the apps. Independent services store data (a PDS), aggregate it into one big stream (a Relay), and turn it into a usable product (an AppView). Bluesky is just the first big app built this way — others share the same identities and data.

The glossary below breaks every one of these terms — and the more technical ones underneath them — into a one-paragraph explanation, with a link to the official spec or docs if you want to go deeper.

Official sources: atproto.com · Official glossary · Bluesky docs