AT Protocol

atproto.com · checked 7 Oct 2026

#3 · Social Media APIs

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How it plugs in

—Public API

NoOpen source

YesFree tier

Signal on Social Media APIs6.4#3 of 20

AT Protocol is an open social protocol for building high-scale social applications that are interoperable by default.

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Runs on

Web
Windows
Mac
Linux
iOS
Android

Facts

Website: atproto.com
Price: Free tier
Free trial: Not stated
App passwords: Accounts can create and revoke app passwords separately from their primary password.
Authentication: Applications can use OAuth, while single-purpose apps such as bots or command-line tools may use password authentication.
Authorization: OAuth is the primary mechanism for clients to make authorized requests to PDS instances, including mobile, browser, desktop, and web service clients.
Cryptography: AT Protocol uses public key cryptography to authenticate public data; protocol-level data encryption is not used, though many components use TLS.
Data model: Users publish JSON records into repositories, and changes to those records sync across the network to drive applications.
Developer support: The official site links to tutorials, SDKs, a cookbook, deployment guidance, and community discussions on GitHub.
Developer use: Developers can build feeds, bots, search engines, and applications using the public firehose, with no API key required.
Hosting limits: Operating a relay is bandwidth intensive, while hosting an AppView is resource intensive.
Identity: Usernames can be domains, and account portability is supported through signed data repositories and DIDs.
Intended users: The protocol is aimed at developers building social applications, agents, custom feeds, and other services using shared network data.
Limited permissions: OAuth lets developers request limited account access without requiring users to share their passwords.
Maker: The site identifies Bluesky Social PBC as the copyright holder.

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