Mattermost vs Slack (2026)
A side-by-side comparison of features, pricing, licensing, and self-hosting.
Bottom line: choose Slack for the most polished chat experience and the biggest app ecosystem; choose Mattermost if data sovereignty, self-hosting, or compliance requirements outweigh UI polish.
Slack set the standard for team chat UX and its integration marketplace covers nearly every SaaS tool a company runs, plus Slack Connect for looping in external partners without a separate account. All of that runs exclusively on Salesforce's cloud — there's no self-hosting option — and per-seat pricing climbs steeply as a team grows, with the free tier capping message history at 90 days.
Mattermost's MIT-licensed core is free to self-host with no seat cap, giving security-conscious teams, government contractors, and regulated industries full control over where messages live, plus built-in compliance and audit logging that Slack reserves for its highest enterprise tier. The trade-off is a UI and mobile experience that still lags Slack's polish, and features like SSO and advanced permissions require Mattermost's paid Enterprise license.
For teams that prioritize onboarding speed and ecosystem breadth, Slack remains the default. For teams that need their chat history and infrastructure entirely under their own control, Mattermost is the more defensible choice.
Mattermost
Open-source, self-hosted team messaging built for security-conscious and DevOps teams.
Pros
- Full data sovereignty — runs on your own servers with no vendor access
- MIT-licensed core is free to self-host with no seat caps
- Built-in compliance, audit logging, and e-discovery features
Cons
- UI and mobile experience lag behind Slack's polish
- Enterprise features like SSO and advanced permissions require a paid license
Slack
Cloud-hosted team messaging and channels platform, owned by Salesforce.
Pros
- Best-in-class UX and near-universal adoption makes onboarding new hires trivial
- Enormous app ecosystem covers almost every SaaS integration
- Slack Connect lets external partners join channels without a separate tool
Cons
- Per-user billing escalates steeply as headcount grows
- Free plan caps message history at 90 days, cutting off institutional memory
Mattermost vs Slack: spec comparison
| Spec | Mattermost | Slack |
|---|---|---|
| License | MIT / Open-core | Proprietary |
| Open source | Yes | No |
| Self-hostable | Yes | No |
| Starting price | Free / self-host | from $7.25/mo |
| Pricing model | open-core | freemium |
| Language | Go | — |
| Platforms | web, ios, android, mac, windows, linux, self-hosted, docker | web, ios, android, mac, windows, linux |
| Founded | 2015 | 2013 |
| GitHub stars | 38,256 | — |
FAQ
Mattermost vs Slack: which is better?
Neither is universally better. Mattermost (Free / self-host) suits Security-conscious engineering teams, government contractors, and enterprises with strict data residency requirements.; Slack (from $7.25/mo) suits Teams that prioritize polish and ecosystem breadth and can absorb per-seat pricing.. The spec table above breaks down the differences.
Is Mattermost or Slack cheaper?
Mattermost starts lower at Free / self-host vs from $7.25/mo.