AT Protocol Reference Implementation

This is the core TypeScript code that powers Bluesky—a decentralized social network. Think of it as the "engine" behind how Bluesky works. Instead of a single company controlling a social network, AT Protocol is an open standard that lets anyone build their own social apps, custom feeds, or alternative clients that all talk to each other safely and securely.

The repository contains multiple building blocks. The main ones are: a client library so developers can connect to the network, security tools for signing and verifying data, identity resolution so you can find other users, and a schema language (Lexicon) that defines how data is structured. There's also a Personal Data Server, which stores a user's posts and data, and an AppView service, which powers features like the main Bluesky timeline. You can think of these like the storage locker and the search index for the social network.

Developers would use this code if they want to build something on top of Bluesky—like a new mobile app, a custom feed algorithm, a moderation tool, or even run their own data server. A creator might want to build a specialized feed showing only posts about music, or a company might want to host their own copy of Bluesky's backend. The key idea is that no single entity controls the network, so third-party developers have the same capabilities as Bluesky itself.

The code is organized as a workspace of separate packages that can be used independently. If you just need to send posts and read data, you can use the client library. If you're building infrastructure, you can use the lower-level cryptography or storage packages. The project includes tests and a way to run a local test environment on your computer, so developers can experiment without touching the live network. The team behind it (Bluesky Social) is selective about accepting changes, prioritizing quality over quantity, and they ask contributors to discuss big ideas before diving into code.