Matrix Synapse

Matrix Synapse is the reference homeserver for the Matrix protocol, an open standard for decentralised, federated, end-to-end encrypted communication. Run your own Synapse instance and you control a chat server that can talk to every other server on the Matrix network, the same way email servers interoperate.

The federation model is the point. Unlike a self-hosted Slack or Mattermost, where your users can only message each other, Matrix users on your server can message anyone on any other Matrix homeserver. Your community stays on your infrastructure while still reaching the wider network. Bridges extend this further, connecting Matrix rooms to Slack, Discord, Telegram, and IRC.

Element is the most polished Matrix client, available on web, desktop, and mobile, but the open protocol means users can choose alternatives. End-to-end encryption protects private and group conversations.

This is rated hard for good reason. Synapse is resource-heavy and complex to operate. It requires a PostgreSQL database, a reverse proxy, and a TURN server for voice and video calls to work reliably. Federation pulls in room state from other servers, which consumes RAM and disk that grow over time. For a casual self-hoster who just wants team chat, Mattermost is far simpler. Synapse is the right choice specifically when federation, the open protocol, and interoperability with the global Matrix network matter more than ease of operation.