AT Protocol
AT Protocol is an open social-web architecture that separates identity, account hosting, data distribution, application views, and moderation. It is the protocol used by Bluesky but is not limited to one application.
Architecture
Each account has a stable DID and a human-readable domain handle. A PDS hosts the account’s signed data repository and manages authentication and writes. Relays aggregate repositories; AppViews build feeds, search, and application behavior; labelers publish moderation judgments.
Account migration is a core design goal. A user can move repository content to another PDS and update the DID document so the same canonical identity points to the new host. The practical independence depends on rotation-key custody, backups, and tool support.
Security and privacy boundary
Signed repositories make public records verifiable. They do not encrypt them. Relays and AppViews are designed to redistribute and index content, and large services can remain concentrated even when PDS hosting is plural. Protocol-conforming deletion propagates account status, but non-conforming downstream copies may persist.
Secure and decentralized communication stacks compares this portability model with ActivityPub federation and Nostr relays.