Self-hosted team chat: Mattermost and Rocket.Chat explained
The two leading open-source Slack alternatives — what they do, how they differ, and when self-hosting team chat makes sense.
If your team wants Slack-style channels but cannot send messages and files through someone else's cloud, the two mature options are Mattermost and Rocket.Chat. Both give you persistent channels, direct messages, file sharing, search, bots and integrations — running on your own server.
Mattermost
Slack-like UX, easy for teams to adopt with almost no retraining.
Strong on compliance and control — self-hosted editions let you keep everything in-house, with audit logs and granular admin controls.
Rich integration ecosystem — incoming/outgoing webhooks, slash commands, and a plugin system; plays well with CI/CD and alerting.
Licensing: the core is open source (MIT/AGPL components) with a commercial enterprise edition adding features on top.
Rocket.Chat
Broader native feature set in the open version — including built-in omnichannel/live-chat with your website visitors, and marketplace apps.
Federation support — Rocket.Chat instances can talk to each other, and it can speak Matrix.
Also open source with a commercial edition for large deployments.
Which one?
Want a Slack clone your team adopts in a day, with excellent integrations? Mattermost.
Want more features out of the box (live chat, marketplace, federation) in the open edition? Rocket.Chat.
Want to chat with people on other servers, not just your own team? Look at Matrix/Synapse instead — see What is Matrix Synapse.
When self-hosting team chat makes sense
Data control — regulated industries, defence, health, legal, or just a policy that internal comms stay internal.
Cost at scale — at a certain headcount, a fixed-cost VPS beats per-user SaaS pricing.
Integration with your own systems — bots that talk to internal APIs are far easier when the chat server is on the same network.
You give up the zero-maintenance convenience of a hosted service, so plan for updates, backups and TLS.
Where to use it, and going live
A 2–4 vCPU, 4 GB VPS handles a small-to-medium team. Both ship as Docker deployments (with an official Mattermost image and Rocket.Chat image). Stand up the app, add a database (PostgreSQL for Mattermost; MongoDB for Rocket.Chat), put TLS in front, then invite the team. Back up the database and any uploaded files. For push notifications to mobile, note both have extra setup (a push proxy or your own notification service) — the web and desktop clients work without it.
Specs and setup: /app-hosting/mattermost, and the Rocket.Chat page alongside it.