Replacing Slack with Mattermost: what really changes for a small business

Slack has become the default reflex for teams. But beyond a handful of people, the per-user bill adds up, and the history of your conversations is hosted outside Europe. Mattermost is the closest open source alternative. Here is what changes, and what does not.

What does not change for your teams

Mattermost follows the same patterns as Slack:

• public and private channels, direct messages and groups;
• threads, reactions, mentions, and history search;
• file sharing and link previews;
• web, desktop and mobile apps;
• integrations through webhooks and bots, compatible with many existing tools.

For a user, getting to grips with it usually takes a morning.

What changes

Your data stays with you

Mattermost is installed on your own server, in France or elsewhere in Europe. Messages, files and logs never leave your infrastructure, which also simplifies GDPR compliance.

The cost no longer depends on the number of users

The free edition of Mattermost has no per-user price. You pay for hosting and maintenance. With Slack Pro, a team of 25 people costs roughly €2,000 a year at the public small-business price, and that amount rises with every hire.

Someone has to look after the server

This is the real trade-off: security updates, backups, monitoring. Either you have someone in-house, or you hand it over to a provider.

How the migration works

1. Export from Slack. Administrators of a Slack workspace can export the history of public channels. Private channels and direct messages depend on the Slack plan you have.
2. Import into Mattermost. The official import tool brings across channels, messages and users.
3. Pilot. One team tests it for a week or two while the others stay on Slack.
4. Switch-over. Everyone moves to Mattermost; the Slack subscription is cancelled at renewal.

What to check before you start

• Critical integrations: list the tools connected to Slack (alerts, CRM, support) and check for their equivalents.
• Calls: Mattermost offers audio calls and screen sharing; for group video calls, it is often paired with Jitsi Meet.
• External access: if you talk to clients through shared Slack channels, plan how you will invite them.

In summary

For a small business, moving from Slack to Mattermost means keeping your habits, taking back control of your data and replacing a growing bill with a fixed cost. The key is a well-prepared migration and a properly maintained server.

Estimate your own savings with the simulator, or request a free audit.