ZulipOrganise team conversations into streams and focused topic threads.
Free and open source (Apache-2.0 licence per GitHub).
Notes, tasks & docs
Mattermost
Free optionBrowser
Coordinate work through channels, messages and shared files.
What you can use it for
Coordinate work through channels, messages and shared files.
- Covers the core everyday task of Slack: team chat.
- 39.3k GitHub stars; last commit 2026-10-15.
Workflow coverage and comparison notes
Host secure team messaging, voice huddles and workflow integration with self-hosted Mattermost instead of Chanty paid team plans.
Before you switch
Limitations not yet documented.
Alternatives to these paid apps
Each comparison covers the workflow described above, rather than every paid feature.
More for the same workflow
See alternatives →Zulip