Atproto

atproto was developed by Bluesky as an open social protocol.

The AT Protocol is a networking technology created to power the next generation of social applications. The initial reference application, bsky.app,provides a global-scale microblogging experience.

Creation of an IETF working group is in progress, as of late 2025 / early 2026.

Protocol Overview

The Authenticated Transfer Protocol, aka atproto, is a federated protocol for large-scale distributed social applications. This document will introduce you to the ideas behind the AT Protocol.

From the Protocol Overview

Specification

The Authenticated Transfer Protocol (AT Protocol or atproto) is a generic federated protocol for building open social media applications. Some recurring themes and features are:

• self-authenticating data and identity, allowing seamless account migrations and redistribution of content
• design for “big world” use cases, scaling to billions of accounts
• delegated authority over application-layer schemas and aggregation infrastructure
• re-use of existing data models from the dweb protocol family and network primitives from the web platform

From the Specification

See also PDS, ATProto Community Resources