What is AT Protocol used for?

AT Protocol is a reference TypeScript implementation of the AT Protocol, the decentralized social protocol behind Bluesky, with SDK packages and Lexicon schemas. It is a good fit for building Bluesky bots and clients, and running or studying federated social services.

Is AT Protocol open source?

Yes. AT Protocol is open source under a custom licence. Its source code is on GitHub at bluesky-social/atproto and is written mainly in TypeScript.

Yes. AT Protocol is open source, so the software itself is free to use under the terms of its own licence.

Can I self-host AT Protocol?

Yes. AT Protocol can be self-hosted on your own server or infrastructure.

What are some alternatives to AT Protocol?

Similar open-source tools in the Social Media category include Bluesky, Misskey and diaspora*. SaaS products in the same category include BeReal, BulletSocial and Donivo.

Is AT Protocol actively maintained?

Yes. The most recent commit to AT Protocol was on 2 October 2026. The project has 9.7k stars on GitHub.

AT Protocol: open-source social media

About AT Protocol

This repository holds Bluesky's reference implementation of the AT Protocol, short for Authenticated Transfer Protocol, along with the backend of the app.bsky microblogging service. The protocol is a decentralized social media standard developed by Bluesky Social PBC, intended so that third-party software can be as capable as first-party software.

Custom feeds, federated services and alternative clients all use the same APIs, so developers are not locked out of the ecosystem. The repo includes the Lexicons, JSON schemas in the Lexicon definition language for the com.atproto and app.bsky namespaces, and TypeScript packages published to npm under the @atproto scope. For apps and bots the README points to @atproto/lex, a type-safe SDK that generates TypeScript from Lexicon schemas, with the older @atproto/api client still available.

The code is written in TypeScript and the license is stated in the repository. Learning resources include an overview and guides, GitHub Discussions and the protocol specifications. It is mainly for developers building clients, bots, feed generators or services on the AT Protocol network.

Key features

Reference implementation of the AT Protocol
Lexicon schemas for com.atproto and app.bsky
Type-safe @atproto/lex SDK
TypeScript packages published on npm
Backend code for the Bluesky service

Good fit for

→Building Bluesky bots and clients
→Running or studying federated social services

Built with: TypeScript
Tags: atproto; bluesky; decentralized; social-network; protocol; typescript; sdk

AT Protocol: questions and answers

What is AT Protocol used for?: AT Protocol is a reference TypeScript implementation of the AT Protocol, the decentralized social protocol behind Bluesky, with SDK packages and Lexicon schemas. It is a good fit for building Bluesky bots and clients, and running or studying federated social services.
Is AT Protocol open source?: Yes. AT Protocol is open source under a custom licence. Its source code is on GitHub at bluesky-social/atproto and is written mainly in TypeScript.
Is AT Protocol free?: Yes. AT Protocol is open source, so the software itself is free to use under the terms of its own licence.
Can I self-host AT Protocol?: Yes. AT Protocol can be self-hosted on your own server or infrastructure.
What are some alternatives to AT Protocol?: Similar open-source tools in the Social Media category include Bluesky, Misskey and diaspora*. SaaS products in the same category include BeReal, BulletSocial and Donivo.
Is AT Protocol actively maintained?: Yes. The most recent commit to AT Protocol was on 2 October 2026. The project has 9.7k stars on GitHub.