Matrix
Matrix is an open standard and decentralized protocol for real-time communication, providing federated messaging, voice, video, and IoT signalling across independently operated homeservers. The Matrix specification defines several REST APIs (Client-Server, Server-Server, Application Service, Identity Service, and Push Gateway) that interoperate across the federation. Authentication is typically performed via Bearer access tokens, with newer flows using OAuth 2.0.
APIs
Matrix Client-Server API
REST API used by Matrix clients to communicate with a homeserver, covering login, room creation and management, message sending, sync, device management, end-to-end encryption, ...
Matrix Server-Server (Federation) API
Federation API that lets Matrix homeservers exchange events, presence, and key information with one another over signed JSON requests.
Matrix Application Service API
API used by application services (bridges, bots) to integrate with a homeserver, claim namespaces, and exchange events.
Matrix Identity Service API
API for looking up Matrix user IDs from third-party identifiers such as email addresses and phone numbers via federated identity servers.
Matrix Push Gateway API
Push Gateway API homeservers use to deliver notifications to mobile push services on behalf of Matrix clients.