Comparison of ActivityPub, AT Protocol, and Matrix Protocol (mainly a reminder for myself) “
| Feature | ActivityPub | AT Protocol | Matrix Protocol |
|---|---|---|---|
| Primary Use Case | Social networking (microblogging, content sharing) | Social networking with algorithmic control | Real-time communication (chat, VoIP) |
| Commands/Verbs | Create, Update, Delete, Follow, Like, Announce (Repost) | Create, Update, Delete, Follow, Like, Repost, Algorithmic Choice | Send, Receive, Join Room, Invite, Leave |
| Data Model | Activity-Object Model in JSON-LD | JSON with user-defined schemas | JSON (events model for real-time updates) |
| Transport Protocol | HTTPS, with JSON-LD | HTTPS, with JSON | HTTP (REST) and WebSocket, with support for end-to-end encryption (E2EE) |
| Identity Management | Tied to server domain (e.g., @user@domain.com), uses WebFinger for discovery | Portable DIDs for decentralized identity | Tied to server domain but portable; user ID format is @user:domain.com |
| Federation | Federated, allowing instances to share content and social connections across domains | Federated with content and algorithm control | Federated, with real-time, synchronized state across servers |
| Interoperability | Widely interoperable with other ActivityPub-compliant platforms in the Fediverse | Designed for custom app experiences, interoperability is in development | Supports interoperability with other Matrix clients; bridges to other protocols (e.g., Slack, IRC) |
| End-to-End Encryption | Not native to protocol but possible with extensions | Not natively specified | Built-in and widely supported, particularly in 1:1 and group chats |
| Moderation | Instance-based moderation policies, customizable filters and blocks | User-level and instance-level moderation, customizable algorithms | Room-level moderation, with granular permissions for room admins |
| Popular Platforms | Mastodon, PeerTube, Pixelfed, WriteFreely | Bluesky Social, upcoming decentralized apps | Element (main Matrix client), Synapse (server), bridges for Slack, Discord, Telegram, etc. |
Summary of Key Differences
- ActivityPub is best suited for federated social networking, particularly for applications that prioritize openness and content sharing across platforms in the Fediverse. It uses an Activity-Object model with JSON-LD and supports instance-based identity.
- AT Protocol focuses on user control over content algorithms and portable identities using DIDs, with a vision for interoperability in custom social applications. It is also designed for federated social networks but with more control over data portability and algorithmic transparency.
- Matrix Protocol excels in real-time, federated communication, supporting secure, encrypted messaging with granular moderation capabilities. It’s heavily used for chat, VoIP, and collaborative tools, emphasizing interoperability with other platforms through bridges.