Said something interesting to a friend today when they asked about different open social web protocols. It might be a little bit controversial, but: I think that ActivityPub is decentralized in principle, whereas AT Protocol is decentralized in practice. 🧵
Jul 21, 2026 at 7:28 PM
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?
ActivityPub, AT Protocol, and more!
Why ActivityPub is the future
We often tout things like “Mastodon is based on open web protocols” as one of its advantages. I want to elaborate why exactly that’s a good thing.
Social Networking Utopia — Matt
In discussing the network topology of social networks — whether centralized like Facebook or federated like ActivityPub — I think the ult...
Seeing the Politics of Decentralized Social Media Protocols
Calls to decentralize feed-based social media have been driven by concerns about the concentrated power of centralized platforms and their societal impact. In response, numerous decentralized social media protocols have emerged, each interpreting “decentralization” in a different way. We analyze four such protocols (ActivityPub, AT Protocol, Nostr, and Farcaster) drawing on protocol documentation, media coverage, direct usage, and semi-structured interviews with protocol developers and experts to situate each protocol within its socio-technical goals. To support this analysis, we develop a grounded lexicon that facilitates the description and comparison of analogous components across each protocol. With it, we show how each protocol distributes control over key components differently, shaping who holds power over critical aspects such as user identity, curation, and infrastructural ownership. By examining protocols as socio-technical artifacts, we show how they prioritize different values and make distinct trade-offs, providing CSCW researchers with a lens to more effectively evaluate and design future decentralized social media systems.
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.
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.
Open Social
Open Social
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
Many people are talking about decentralized social media protocols like #ActivityPub and #ATProto and all the amazing things one can do with them. But do you actually know how they work? We thought we'd do something about this. Come to #FediForum next week if you are curious and like to find […]
Original post on mastodon.social
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