Overview

Mattermost is a powerful, open-source team communication platform built as a self-hosted alternative to Slack. Instead of sending your conversations through someone else’s servers, you deploy Mattermost on your own hardware and keep every message, file, and integration under your control. It powers focused, secure collaboration for teams that need speed and sovereignty — from small development squads to enterprises with strict compliance requirements.

The open-source core — Mattermost Team Edition — is free to use and MIT licensed. It combines familiar channel-based messaging with enterprise-grade tooling, deep DevOps integrations, and full data ownership.

Key Features

• Self-hosted messaging: run the server as a single Linux binary with PostgreSQL and keep all data on systems you control
• Channels and direct messages: organise team conversations just like Slack, with threads, mentions, pinned messages and search
• Developers-first integrations: webhooks, slash commands, bots, and native GitLab/GitHub integration for DevOps workflows
• Voice and video calls: built-in audio and video conferencing alongside text channels
• Compliance and audit: granular permissions, retention policies, audit logs and data archiving for regulated environments
• Cross-platform clients: desktop apps for Windows, macOS and Linux, plus web and iOS/Android mobile clients

Why Use It

If you want the familiar Slack experience without surrendering your data, Mattermost is one of the most proven choices. Because it is genuinely open source and MIT licensed in its Team Edition, you can self-host it free of charge, customise the source, and wire it directly into your build, deploy and alerting pipelines.

Use Cases

• Self-hosted team chat for organisations that cannot send internal communication to the cloud
• Security-conscious DevOps and engineering teams that want chat tightly coupled to their toolchain
• Air-gapped or on-prem deployment where external SaaS messaging is not permitted

Platforms

Server on Linux (single binary with PostgreSQL); desktop clients for Windows, macOS and Linux; mobile apps for iOS and Android

Licence

MIT (open-source Team Edition); commercial Enterprise and Professional editions also available

Website

mattermost.com