Mattermost vs Slack: Complete Comparison 2026
An in-depth comparison of features, pricing, and user experience to help you make the right choice.
Mattermost
8.5(4,100 reviews)
Open-source, self-hostable team messaging built for security-conscious teams who need full data control.
Slack
Channel-based messaging app for teams, with threads, huddles, app integrations and searchable history.
Quick Comparison
| Aspect | Mattermost | Slack |
|---|---|---|
| Best For | Government agencies and defense contractors with data residency rules | Startups and tech teams that run on many SaaS tools |
| Pricing Model | Open Source | Freemium |
| Starting Price | Free | Free |
| Deployment | self hosted, on premise, cloud, hybrid | cloud |
| Platforms | WEB, WINDOWS, MAC, LINUX, IOS, ANDROID | WEB, WINDOWS, MAC, LINUX, IOS, ANDROID |
| Rating | 8.5/10 | 9.0/10 |
Pros & Cons
Mattermost
Pros
- Fully self-hostable, including air-gapped networks with no internet
- Open-source core you can audit, fork and extend
- Strong fit for developer, DevOps and incident-response workflows
- Full REST API and plugin framework for custom integrations
- Free self-hosted edition has unlimited users and message history
Cons
- You own hosting, upgrades, backups and security patches
- SSO and compliance exports require paid Enterprise tiers
- Integration directory is far smaller than Slack's
- Interface is less polished than commercial competitors
- Initial setup needs real IT and DevOps expertise
Slack
Pros
- Best-in-class app directory with 2,600+ integrations
- Search is fast and accurate across years of history
- Channels and threads keep conversations organized and scannable
- Workflow Builder enables no-code automation without IT
- Polished desktop and mobile apps that feel fast
Cons
- Free plan limited to 90 days of message history
- Per-user pricing gets expensive for large teams
- Always-on notification culture can hurt deep focus
- Microsoft Teams comes bundled free with Microsoft 365
- No built-in document or project management depth
Pricing Comparison
| Product | Pricing Model | Starting Price |
|---|---|---|
| Mattermost | open source | Free0 |
| Slack | freemium | Free0 |
Our Verdict
Choose Mattermost if...
Government agencies and defense contractors with data residency rules
Choose Slack if...
Startups and tech teams that run on many SaaS tools
Still Not Sure?
Explore more alternatives or read in-depth reviews to make your decision.