







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
mastodon.socialApr 20, 2026 at 5:42 PM
atproto academy
Your resource for learning the decentralized social networking protocol powering the future of social media.
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?

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.

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.
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.
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.
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...
#protocolsforpublishers #atproto #mcp #webapplets | Chad Kohalyk
Web publishing is facing its next challenge: a new iteration of centralizing platforms. BUT there is also a new wave of open protocols and standards that can help us gain our independence. Next month in NYC we are gathering a group of frontier technologists and popular web publishers to discuss how we can sail into this next platform shift as captains. #ProtocolsForPublishers Learn more and sign up here: https://pfp.unternet.co We will be hosting talks on #atproto #mcp #webapplets and web payments, and give publishers the opportunity to interact directly with developers working on these frontier technologies. Thank you to Unternet, Graze Social, Free our Feeds, and betaworks for their support.
What is atproto?
What is atproto? atproto is two things: A protocol for creating open social networks An open social network atproto, the open social network Today the atproto network has 36+ million users and powers Bluesky and a handful of other apps. Almost all atproto data is public. Content like posts, likes, follows, and photos/videos are publicly accessible to any network participant in a permissionless way. As an example of how open the network is, here’s how easy it is to stream all public data on the network using a public atproto Relay like bsky.network:

ActivityPub Client API: A Way Forward | Steve Bate
The ActivityPub Client-to-Server (C2S) protocol was envisioned as a cornerstone of the decentralized social web, along with the Server-to-Server (S2S) protocol. Standardized by the W3C in 2018, C2S defines how user-facing applications, such as mobile apps or web clients, and bots should interact with social servers using Activity Streams 2.0 and JSON-LD. In theory, it ... Read more

We're so excited to support @thisismissem.social's work bringing FedCM to the open social web! atproto.com/blog/working-to-decentralize-…
Working to Decentralize FedCM - AT Protocol
atproto.comSome of us in the ActivityPub world feel jealous of AtProto’s success (like me). But more decentralization is a win for everyone. With Bridgy from @anew.social connecting protocols, this isn’t competition, it’s momentum. We’re stronger together, so let’s build the social web humanity deserves 🚀
Stratos
Permissioned Data Diary 3: Your Bucket, My Data - Daniel's Leaflets
Permissioned Data Diary 2: Buckets - Daniel's Leaflets
Spaces as Layers - Nick's Blog