lørdag, March 28, 2026
Briefly about ActivityPub
ActivityPub is an open, decentralized social networking protocol. Think of it as a universal "language" that enables different social media platforms – such as Mastodon (microblogging), Pixelfed (images) and PeerTube (video) – talking together.
ActivityPub is a protocol developed by the the World Wide Web Consortium (W3C), the international non-profit organization that develops open standards and guidelines to ensure that the Internet works consistently for everyone.
The core concept: "Fediverse"
When a platform uses ActivityPub, it becomes part of what is called Fediverse (a "federated universe"). This means you can follow someone on a completely different platform just as easily as if they were on your own.
* Example: A Mastodon user can follow a Pixelfed user and see that person's photos directly in their own Mastodon feed.
How does it work?
ActivityPub is based on a standard called ActivityStreams, which uses the JSON format to describe social actions. It works in two layers:
1. Server-to-Server (Federation): Allows different servers to share information and send notifications to each other.
2. Client-to-Server: Allows apps (on your phone or computer) to communicate with your account on the server to post or read content.
Key components:
* Actors: Entities that perform actions (users, bots or groups).
* Inbox & Outbox: Each actor has a unique address (URL) to receive messages (Inbox) and send them (Outbox).
* Activities: The actions themselves, such as "Create" (a post), "Follow" or "Like".
Why is it important?
* Decentralization: No single company (like Meta or X) owns the entire network. Everyone can run their own server.
* Data Ownership: Users generally have more control over their own data and can move to another server without losing connection to their friends.
* Cohesion (Interoperability): It breaks down the "closed gardens" so you can choose the software you like best and still be in touch with everyone else.
Visit W3Cs own description of ActivityPub here
