US · United States
Free (10k msg history) · Self-host free · Cloud from $6.67/user/mo
Zulip
Replaces: Slack, Microsoft Teams
Open-source team chat organized by topic threads so async conversations never get buried in noisy channels.
The Catch (read before switching): Topic-based threading takes a few days to learn if your team is used to Slack-style flat channels.
Hard Constraints Checklist
- Open SourceYes
- Self-HostableYes
- Permanent Free TierYes
- Headquartered Outside USNo
- Zero Tracking / E2EEYes