







Christine Lemmer Webber is lead author and co-editor of the W3C ActivityPub specification. Daniel Holmgren is Head of Protocol at Bluesky, working on the AT Protocol specification at the IETF. Join us for a discussion on decentralization trade-offs and other design decisions in the two protocols, and what that means for different architectures, structures, and even future points of convergence. Moderated by Boris Mann
Protocol Reader - Summer of Protocols
The Protocol Reader The Protocol Reader is an 358-page book (currently only available as an epub) comprising 26 foundational essays by 31 authors from the Summer of Protocols program, carefully edited and sequenced to introduce you to the fascinating new discipline of Protocol Studies. It can serve as

AT Protocol
The AT Protocol is a protocol and set of open standards for decentralized publishing and distribution of self-authenticating data within the social web. It serves as the technical foundation of the Bluesky social network, originally developed as a reference implementation for the protocol, as well as an ecosystem of interoperable social applications and services collectively referred to as the ATmosphere.
Introduction to AT Protocol
Walkthrough of the various parts and concepts in Bluesky's AT Protocol (ATProto), the types of servers involved and how it all fits together

Introduction to AT Protocol
Walkthrough of the various parts and concepts in Bluesky's AT Protocol (ATProto), the types of servers involved and how it all fits together

Appendix:Xanadu - AT Protocol Paper Errata and Details
A description of known problems in Bluesky PBC's paper, "Bluesky and the AT Protocol: Usable Decentralized Social Media", as well as notes on terminology changes and how Bluesky's implementation differs from that described in the paper.
FEP-1042: Peer to Peer Fediverse Identities
Hey folks, we at [Distributed Press](https://distributed.press) have been working on making a bridge between peer to peer or "dweb" protocols and ActivityPub implementations over the past year and wanted to solidify our approach so that others can interoperate. Here's is an initial draft expla...
ActivityPub, AT Protocol, and more!
Talking about this article and how ActivityPub and AT Protocol are maybe not as different as people might think. We covered some slides to an unrecorded talk of mine, which explores a lot of things...
Protocol: How Control Exists after Decentralization by …
How Control Exists after Decentralization by Galloway, …


ActivityPub, AT Protocol, and more!
ATPROTO isn’t just for Bluesky weiners
ActivityPub
ActivityPub is a protocol and open standard for decentralized social networking. It provides a client-to-server (C2S) API for creating and modifying content, as well as a federated server-to-server (S2S) protocol for delivering notifications and content to other servers. ActivityPub is the defining standard of the Fediverse, a decentralised social network of various social interaction models, and content types, which consists of independently managed instances of software such as Mastodon, Pixelfed and PeerTube, among others.
Bluesky and the AT Protocol: Usable Decentralized Social Media
Bluesky is a new social network built upon the AT Protocol, a decentralized foundation for public social media. It was launched in private beta in February 2023, and has grown to over 10 million registered users by October 2024. In this paper we introduce the architecture of Bluesky and the AT Protocol, and explain how the technical design of Bluesky is informed by our goals: to enable decentralization by having multiple interoperable providers for every part of the system; to make it easy for users to switch providers; to give users agency over the content they see; and to provide a simple user experience that does not burden users with complexity arising from the system's decentralized nature. The system's openness allows anybody to contribute to content moderation and community management, and we invite the research community to use Bluesky as a dataset and testing ground for new approaches in social media moderation.

Federation Architecture | Bluesky
The AT Protocol is made up of a bunch of pieces that stack together. Federation means that anyone can run the parts that make up the AT Protocol themselves, such as their own server.
