ActivityPub

Federated Protocol

W3C Recommendation for decentralized social networking based on ActivityStreams 2.0, providing standardized client-to-server (C2S) and server-to-server (S2S) APIs for creating, updating, and deleting content as well as federating social activities across independently operated servers

Padrão Aberto
Links
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Detalhes

Licença W3C Standard (implementations vary: Mastodon AGPL-3.0, Pleroma AGPL-3.0, Pixelfed AGPL-3.0, Lemmy AGPL-3.0, PeerTube AGPL-3.0, others MIT/Apache)
Status de Dev 🟢 Ativo
Detalhe do Status de Dev Released (W3C Recommendation, January 23, 2018; widely implemented; Fediverse ecosystem with 10M+ accounts across thousands of instances)
Proprietário W3C Social Web Working Group (original authors: Christopher Lemmer Webber, Jessica Tallon, Erin Shepherd, Amy Guy, Evan Prodromou); now maintained by W3C Social Web Community Group
País International (W3C standard)
Ano de Início 2016
Stack Implementation-dependent (Mastodon: Ruby on Rails + Node.js; Pleroma/Akkoma: Elixir; Pixelfed: PHP/Laravel; Lemmy: Rust; PeerTube: TypeScript/Node.js)
Financiamento W3C (standards development funded by W3C member organizations); implementations funded separately (Mastodon: donations + EU grants; Pixelfed, Lemmy, PeerTube: donations/grants)
Última Investigação 15 de jan. de 2026

Domínios de Caso de Uso

Communication Group Formation & Governance Events & Coordination

Capacidades

Protocol federation Cross-instance federation Consent-based audiences

Federated Protocol Atributos

Origins Social networking / Federation (evolved from OStatus, Pump API, and earlier W3C Social Web Working Group work; ActivityStreams 2.0 as data model foundation)
Database Implementation-dependent (typically PostgreSQL; Mastodon uses PostgreSQL + Redis + Elasticsearch)
Query Language N/A (servers expose HTTP APIs per ActivityPub spec; no standardized query language; Linked Data Notifications for inbox delivery)
Data Formats JSON-LD (ActivityStreams 2.0 vocabulary; Activity, Actor, and Object types; compacted JSON-LD with @context)
Collaborative Live Editing N/A (designed for asynchronous social federation; not a collaborative editing protocol)
Rich Text Editing Application-level (clients typically support HTML/Markdown in content fields)
Mobile Support Yes (Mastodon iOS/Android, Tusky, Fedilab, Ice Cubes, Ivory, Pixelfed, etc.)
Web Support Yes (Mastodon Web, Pixelfed, Lemmy, PeerTube, BookWyrm, etc.)
Native Apps Yes (desktop and mobile clients across implementations)
Terms Self-hosting + Free public instances + Paid hosting services (e.g., masto.host, federation.spacebear.ee)
Funds N/A (standard development funded by W3C; Mastodon gGmbH separately funded)
Based On ActivityStreams 2.0 (W3C Recommendation, data model); evolved from OStatus (Salmon, PubSubHubbub, Atom) and Pump API (pump.io by Evan Prodromou)
Content Addressing No (location-based via HTTP URIs; not content-addressed)
E2EE N/A (not part of the ActivityPub standard; some implementations exploring E2EE for direct messages)
Signature HTTP Signatures (server-to-server authentication; signing HTTP requests with RSA or Ed25519 keys for federation; Linked Data Signatures also used by some implementations)
Permissions Server-based ACLs (to, cc, bcc addressing for audience targeting; public, unlisted, followers-only, direct visibility levels in Mastodon)
Semantic Web Compatibility JSON-LD / ActivityStreams 2.0 (built on semantic web standards; uses @context for linked data; Activity, Actor, Object types defined in AS2 vocabulary)
Federation Model Server-to-Server (S2S) via HTTP POST to Actor inboxes; servers deliver Activity objects to followers' inboxes and shared inboxes; Client-to-Server (C2S) API also specified but less commonly implemented
Instance / Server Requirements Moderate (can run on VPS; Mastodon: ~2GB RAM, ~20GB storage minimum; scales with user count and federation breadth)
Account Portability Partial (follower migration supported via Move activity; content/posts stay on origin server; Mastodon supports account redirect and follower transfer)
Discovery / Relay Architecture Instance-based discovery (WebFinger for user lookup; Actor URIs for profile resolution) + optional relays for content distribution across instances
Server Authority Model Full server authority (instance admins control users, content moderation, federation policy; can defederate from other instances; to/cc/bcc addressing for audience targeting)
Protocol Maturity / Standardization W3C Recommendation (January 23, 2018; formal W3C standard; ActivityStreams 2.0 also a W3C Recommendation)
Data Sovereignty Server-controlled (users' data stored on home instance; server admin has full access; user depends on instance operator)