The Secure CommsOS™ for mission-critical operations
Channels, threads and federation, self-hosted.
- Language
- TypeScript
- Licence
- Other
- Stars
- 46k
- Latest
- 9.0.0
- Last push
- 2026-11-12
alternative to Slack, Microsoft Teams
Mattermost
Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
Conversations split into topics inside each channel.
- Language
- Python
- Licence
- Apache-2.0
- Stars
- 26k
- Latest
- 12.4
- Last push
- 2026-11-11
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- v12.1.02026-11-05Mattermost Platform Release 12.1.0pre-release
- v12.1.0-rc42026-11-05Mattermost Platform Release 12.1.0-rc4pre-release
- v11.7.152026-11-05Mattermost Platform Extended Support Release 11.7.15 contains Low to High severity level security fixes.
- v11.11.42026-11-05Mattermost Platform Release 11.11.4 contains Medium to High severity level security fixes.
- v11.10.52026-11-05Mattermost Platform Release 11.10.5 contains Medium to High severity level security fixes.
✓ signed The latest release, v12.0.2, carries a signature GitHub verified.
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- SlackChannels, threads and calls on your own server, with an importer for Slack exports. Migration notes → Official migration guide ↗Full replacement
- Microsoft TeamsChat and calls on your own server, without the Microsoft 365 integration.Partial