head to head
Slack vs Mattermost
Mattermost is the open source alternative to Slack — channel-based team messaging platform. Here is the honest comparison.
Yes — Mattermost is a viable free replacement for Slack. Mattermost is open source under its own open-source terms, written in TypeScript, with 39,093 GitHub stars, 9,000 forks and 1,012 open issues; it was last pushed 3 hours ago. Slack costs from $8, while self-hosting Mattermost carries no licence fee — the trade is your operational time instead of a subscription. 3 other open source Slack alternatives are tracked here, led by Jitsi at 29,931 stars. Mattermost ranks #1 of 4 tracked open source Slack alternatives by stars. The tracked set, by adoption: Jitsi (29,931 stars), Zulip (25,921 stars), Element (13,461 stars). Replacement criteria on this page: 4 reasons to move to Mattermost and 3 reasons to stay on Slack.
choose Mattermost if
- Your Slack bill is growing with seats or usage
- You need your data in a format and server you control
- Your compliance posture requires auditing the code that touches sensitive data
- You have (or can rent) a server and basic Docker comfort
stick with Slack if
- You need the polished onboarding and support SLAs of a commercial vendor
- Your team has zero capacity to operate software, even self-hosted-simple
- You depend on a Slack integration ecosystem that the OSS alternatives have not replicated
Side by side
| Mattermost (open source) | Slack | |
|---|---|---|
| Price | Free (self-hosted) | $8.75-$12.50/user/month |
| License | Custom / other | Proprietary |
| Source code | Public, auditable | Closed |
| Self-hosting | Yes — mattermost/mattermost | Cloud only |
| Data ownership | Your server, your format | Vendor's cloud |
| Community | ★ 39K · ⑂ 9.0K | — |
| Built with | TypeScript | — |
Why people look for a Slack alternative
About Mattermost
Mattermost is an open core, self hosted collaboration platform for teams that need secure chat, workflow automation, voice calling, screen sharing, and AI integration while keeping the deployment under their own control.
read the full Mattermost overview →
Other open source alternatives to Slack
last updated nightly · ranking method: github stars, live-tracked
Frequently asked questions
Is Mattermost a good replacement for Slack?
Mattermost is an open source alternative to Slack (Channel-based team messaging platform). It is written in TypeScript and licensed under its own terms, with 39,093 GitHub stars.
Is Mattermost free compared to Slack?
Yes. Mattermost is open source — there is no licence fee, and you can self-host it. Slack is typically a paid subscription, so the trade-off is licence cost against the operational work of running it yourself.
How do I migrate from Slack to Mattermost?
Migration effort depends on the data formats involved. Check Mattermost's documentation for import options, and compare the feature table above to confirm the capabilities you depend on are covered before switching.