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...

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.

A conceptual model of ATProto and ActivityPub

If you were to design an open social networking protocol, what would that look like? Which metaphors and comparisons would you use to get a general idea of how the network functions? And what would you answer if people ask if your network is decentralised and federated?

FediForum Talk: How To Bullshit Your Way Through a Conversation about ActivityPub

By Evan Prodromou, Social Web Foundation and editor of the ActivityPub standard. One of the best bluffers in the field of distributed social networks gives you just enough knowledge about ActivityP...

ActivityPub

The ActivityPub protocol is a decentralized social networking protocol based upon the [ActivityStreams] 2.0 data format. It provides a client to server API for creating, updating and deleting content, as well as a federated server to server API for delivering notifications and content.

Decentralization Trade Offs in AT Protocol and ActivityPub DWeb Camp 2026

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

Off Protocol - AT Protocol

A podcast about the AT Protocol and the open social web.

How decentralized is Bluesky really? -- Dustycloud Brainstorms

Recently due to various events (namely a lot of people getting off of X-Twitter), Bluesky has become a lot more popular, and excitement for its underlying protocol, ATProto, is growing. Since I worked on ActivityPub which connects together Mastodon, Sharkey, Peertube, GotoSocial, etc, etc, etc in the present-day fediverse, I often get asked whether or not I have opinions about ATProto vs ActivityPub, and the answer is that I do have opinions, but I am usually head-down focused on building what I hope to be the next generation of decentralized (social) networking tech, and so I keep to myself about such things except in private channels.

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.