Matrix Protocol
Matrix is the modern alternative to XMPP for federated messaging: bridges to Discord/Slack/WhatsApp, end-to-end encryption by default, and full decentralization. Used by the German government, French public sector, and Mozilla.
What It Defines
Matrix is an open standard for decentralized, federated real-time communication. Rooms are replicated across homeservers using a directed acyclic graph (DAG) of events. The spec defines Client-Server API (sync, messages, rooms), Server-Server Federation API, Application Service API, and end-to-end encryption (Olm/Megolm). Element is the primary client.
Canonical (Normative)
Convenient (Practical)
Related References
Non-profit foundation that stewards the Matrix open standard for decentralized real-time communication. Publishes the Matrix Specification including Client-Server API, Server-Server Federation API, Application Service API, and Push API. Element (formerly Riot) is the reference client.
Related Specs
XMPP powers enterprise messaging (Cisco Jabber), IoT device management, and many open federated chat systems. WhatsApp internally uses a modified XMPP protocol for message delivery.
The roster and subscription model in RFC 6121 defines how federated chat contacts work. Essential for implementing XMPP clients, servers, or S2S (server-to-server) federation between XMPP deployments.