AT Protocol — Decentralized Social Networking Framework by Bluesky

Introduction

The AT Protocol (Authenticated Transfer Protocol) is an open, decentralized framework for social networking. Created by the Bluesky team, it provides the foundation for building federated social apps where users own their data and identity.

What AT Protocol Does

• Provides decentralized identity via DID (Decentralized Identifiers)
• Enables data portability so users can move between service providers
• Defines a schema system (Lexicon) for typed API contracts
• Supports federated data sync across Personal Data Servers
• Powers the Bluesky social network as its reference implementation

Architecture Overview

AT Protocol uses a layered architecture: Personal Data Servers (PDS) store user repositories, Relay services aggregate data streams, and App Views index content for specific applications. Identity is anchored to DIDs, and data is organized as signed, content-addressed records in user repositories.

Self-Hosting & Configuration

• Run your own PDS: npx @atproto/pds init to set up a personal data server
• Configure domain handles for custom user identities
• Deploy behind a reverse proxy with TLS for production use
• Connect to the Bluesky relay network or run a private federation
• Use the TypeScript SDK for building custom AT Protocol apps

Key Features

• True data portability: move your account between providers with history intact
• Cryptographic identity that does not depend on any single server
• Open Lexicon schema system for defining custom record types
• Built-in moderation and labeling infrastructure
• Active ecosystem with the Bluesky app as the primary consumer

Comparison with Similar Tools

• ActivityPub (Mastodon) — different federation model; AT Protocol emphasizes data portability
• Nostr — minimalist relay protocol; AT Protocol has richer schemas and identity
• Matrix — focused on messaging; AT Protocol targets social networking
• Farcaster — crypto-based social; AT Protocol is blockchain-optional
• RSS — read-only syndication; AT Protocol supports full social interaction

FAQ

Q: Do I need to run my own server to use AT Protocol? A: No. You can use Bluesky's hosted PDS. Self-hosting is optional for advanced users.

Q: Is AT Protocol tied to Bluesky? A: Bluesky developed it, but the protocol is open and any app can build on it independently.

Q: Can I migrate my Bluesky account to a self-hosted PDS? A: Yes. Account migration with full history is a core protocol feature.

Q: What languages have SDK support? A: The official SDK is TypeScript. Community SDKs exist for Python, Go, Rust, and others.

Sources

• https://github.com/bluesky-social/atproto
• https://atproto.com