Matrix
Matrix is an open protocol for federated real-time communication and shared room state. Users belong to homeservers, and homeservers exchange room events through federation.
Architecture
A room may span many homeservers. Participating servers replicate persistent events, retrieve history and missing state, and synchronize membership and device information. This supports organizational autonomy, bridges, and rich collaboration. It also distributes metadata and operational trust across the servers represented in a room.
Security boundary
Matrix E2EE uses Olm for device-to-device sessions and Megolm for group messages. Encryption is enabled at room level and depends on compatible clients, device verification, key sharing, backup, and recovery behavior.
Encrypted payloads remain opaque to homeservers, but federation still reveals room participation, server relationships, event timing, device-key activity, and other routing information. Bridges can introduce additional trust boundaries or terminate E2EE.
Secure and decentralized communication stacks explains why Matrix is a strong federated collaboration substrate without being a metadata-private messenger.