Slack vs Mattermost
Overview
Slack is the leading proprietary team messaging platform offering rich integrations and a polished UI. Mattermost is an open-source alternative built specifically for developer and DevOps teams, offering a familiar Slack-like experience with full self-hosting control.
Key Differences
- Cost: Slack costs $7.25–$15/user/month; Mattermost self-hosted is free with optional paid support
- Deployment: Mattermost can be deployed on your own servers, private cloud, or air-gapped environments
- DevOps integration: Mattermost has deeper native CI/CD and DevOps workflow integration than Slack
- Data control: All messages stay on your infrastructure with Mattermost; Slack data lives on third-party servers
- Customization: Mattermost's open-source codebase can be modified; Slack's cannot
Pricing Comparison
| Aspect | Slack | Mattermost |
|---|---|---|
| Base pricing | $7.25–$15/user/month | Free (self-hosted) |
| License | Proprietary | MIT / AGPL |
| Self-hosting | ❌ Not available | ✅ Available |
| Cost at 50 users | ~$362/month | $0/month (self-hosted) |
| Cost at 200 users | ~$1,450/month | $0/month (self-hosted) |
| Vendor lock-in | High | None |
Pros and Cons
Slack
Pros:
- Polished, professionally designed user interface
- Large ecosystem of official integrations
- Managed infrastructure — no server maintenance required
- Enterprise SLA and dedicated support available
- Mobile apps are well-maintained and reliable
Cons:
- Significant per-user monthly cost that scales linearly with team size
- Your data is stored on the vendor's infrastructure
- No ability to inspect or modify the source code
- Feature roadmap controlled entirely by the vendor
- Risk of pricing changes, acquisition, or discontinuation
Mattermost
Pros:
- Free to self-host — costs only server infrastructure
- Complete data ownership and privacy control
- Source code is auditable and modifiable
- Active open-source community
- No vendor lock-in or risk of sudden pricing changes
📦 GitHub: mattermost/mattermost · ⭐ ~30k stars
Cons:
- Requires technical knowledge to self-host and maintain
- May lack some advanced features found in the proprietary version
- Support relies on community forums rather than a paid helpdesk
- UI polish may lag behind the proprietary tool
- You are responsible for updates, backups, and security patches
When to Choose Each
Choose Slack if: Slack is best when your team prioritizes ease of onboarding, has a large budget, and wants the widest ecosystem of third-party app integrations.
Choose Mattermost if: Mattermost excels for engineering teams, regulated industries (healthcare, finance, defense), or organizations needing air-gapped deployment and custom integrations.
Migration Path
Mattermost provides an official Slack import script. Export your Slack workspace data, run the importer, and recreate your integrations using Mattermost's equivalent webhook and bot APIs.
Data sourced March 2026. Pricing and features change — verify at Slack and Mattermost before making decisions.
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