Mattermost vs Zulip
Both are free/open-source alternatives to Slack. Here's how they stack up — verified facts, no spin.
Mattermost
TOP PICKSelf-hosted team chat built for security-conscious orgs.
Mattermost is an open-source, self-hostable Slack alternative with strong security and compliance features, popular with engineering and defense/regulated teams that need to own their data.
Zulip
Threaded team chat that keeps conversations organized.
Zulip is an Apache-2.0 open-source chat app whose topic-based threading model keeps busy teams' discussions searchable and organized. Self-host it or use the hosted option.
Side by side
| Mattermost | Zulip | |
|---|---|---|
| Sovereignty Score | 88 | 88 |
| Open source | Yes | Yes |
| Self-hostable | Yes | Yes |
| Local-first | Yes | Yes |
| License | AGPL-3.0 | Apache-2.0 |
| Pricing | Free self-host; paid Enterprise | Free self-host; paid cloud |
Mattermost is Macrostack's recommended Slack alternative, so it's our pick here.
Mattermost
Strengths
- +Purpose-built self-hosted Slack replacement
- +Strong security/compliance story
- +Familiar channel UX
Trade-offs
- −You operate the server
- −Some features are Enterprise-only
Zulip
Strengths
- +Excellent threading model
- +Permissive Apache-2.0 license
- +Great for async teams
Trade-offs
- −Threading is a mental-model shift
- −Smaller ecosystem than Slack
More Slack head-to-heads
Facts verified 2026-07-04. Licenses and pricing change — spotted something out of date? That's a correction we want.