We Replaced Slack with Mattermost and Saved $500 a Year

Slack is good but twelve dollars per person per month adds up fast, a team of ten pays fourteen hundred and forty dollars a year just for chat, and the free plan only shows you the last ninety days of messages so searching for something from six months ago prompts you to upgrade to pro. Mattermost is Slack on your server, open source and self-hosted with unlimited history and all the features teams actually use.

The Docker setup needs Mattermost and a Postgres database because all the message history and user data needs persistent storage. You set environment variables for the database connection, run docker compose up, open port eighty sixty-five, and create your team. The setup is straightforward and the first run initializes the database schema automatically.

Mattermost has native apps for Windows and Mac and Linux and iOS and Android that connect to your server URL. The desktop app supports multiple server connections which is useful if you have a work Mattermost and a personal one. The mobile app sends push notifications through Mattermost’s notification service or you can run your own push proxy if you want full control.

Migrating from Slack is handled through the import feature. You export your data from Slack’s settings, then import it into Mattermost through the system console. Your channels and messages and files and user history all migrate over. I did this for our team and three years of Slack history imported cleanly with nothing lost.

The plugin marketplace adds integrations for GitLab and Gitea for commit notifications, Jitsi for video calls, webhooks for connecting anything including n8n and monitoring alerts, and Zoom for meeting integration. The webhook integration is the most powerful because you can have Uptime Kuma sending alerts to a Mattermost channel and n8n sending daily summaries and Gitea sending pull request notifications, all in one place.

Message retention and compliance are where Mattermost beats Slack for teams that need control over their data. You control how long messages are kept and you can export all messages for compliance without paying extra. Mattermost generates CSV files of all messages on a schedule you configure.

Mattermost replaced Slack for my team and the only difference is we host it ourselves with the same features and same integrations and unlimited history. Your team chat should not hold your history hostage.

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