Mattermost
FreemiumOpen source Slack alternative
About Mattermost
Mattermost is an open-source, self-hostable Slack alternative written in Go and React. The Community edition is MIT licensed; Cloud starts at $10/user/mo; Enterprise licensing adds compliance and SSO. Around 30K GitHub stars. Self-hosting on Linux with Docker is well-documented — Postgres backend, straightforward setup, active update cadence. The messaging model mirrors Slack: channels, DMs, threads, slash commands, and integrations via webhooks and a plugin marketplace. The main advantage over Slack is data sovereignty: messages stay on your servers, which matters for regulated industries (healthcare, finance, government). Compared to self-hosted Rocket.Chat, Mattermost is faster and more reliable. Compared to Zulip, it has better mobile apps but Zulip has a superior threading model for async teams. The Enterprise plan adds SAML SSO, compliance exports, and custom retention policies. Reddit DevOps communities recommend Mattermost for teams with GDPR constraints or air-gapped network deployments where messages cannot leave the organization infrastructure. For public communities, Discord free tier makes more sense. Mattermost is the right call for engineering teams where data residency is a hard compliance requirement.
Key Features
Pricing Plans
Verified April 2026Free (Self-hosted)
- Unlimited users
- Unlimited message history
- File sharing
- Native apps
Professional
- SSO with SAML
- Guest accounts
- Custom retention
Enterprise
- AD/LDAP groups
- Compliance exports
- Custom terms of service
Pros
- Complete data sovereignty with self-hosted deployment
- Open source with no vendor lock-in
- Slack-like familiar interface
- Air-gapped deployment possible for high-security orgs
- Strong compliance and audit logging
- Active community and development
Cons
- Self-hosting requires significant DevOps expertise
- Mobile apps noticeably inferior to Slack/Teams
- Smaller app ecosystem than commercial alternatives
- Complex initial setup
- Performance depends heavily on server resources
Best For
- Organizations requiring on-premise/air-gapped deployment
- DevOps teams needing ChatOps capabilities
- Security-sensitive industries (defense, finance)
- Organizations with strict data sovereignty requirements
Not Ideal For
- Teams without DevOps resources to manage servers
- Organizations wanting polished mobile apps
- Small teams without IT infrastructure
Potential Deal Breakers
- Requires dedicated DevOps resources to maintain
- Mobile experience significantly inferior to competitors
Data & Privacy
Open-source and self-hostable. Self-hosted deployments keep all messages on your infrastructure. Cloud version hosted in US. No AI training on customer messages. Compliance exports available. SOC 2 certified for cloud.
Who Is This For?
Hands-on tested May 2026
Signup Experience
Self-hosted: download Docker image or use the install script, configure database, and the server is running in under 30 minutes on any Linux box. Cloud signup is email only -- workspace live in under a minute. The gap in setup effort between the two is enormous.
For Home Users
Free self-hosted Mattermost is a legitimate Slack replacement for family or friend groups who want to own their chat data. Requires someone comfortable with a server or a cheap VPS -- if that fits, the zero monthly cost is compelling.
For Business Users
Free self-hosted tier covers most small teams. Professional at $10/user/mo adds guest accounts, compliance exports, and advanced permissions. The core value proposition is data sovereignty -- regulated industries and security-conscious teams use Mattermost specifically because chat data never leaves their infrastructure. Slack is more polished and has better integrations, but Mattermost wins on control.
What Users Say
“"Mattermost is the only option when you need true on-prem with no data leaving your servers."”
— Reddit user
“"Great for security-conscious organizations. Painful to set up but worth it for compliance."”
— Reddit user
“"We use it instead of Slack for regulated industry compliance. Would never go back to cloud-only."”
— Reddit user
Our Verdict
Mattermost is the best option for organizations that absolutely cannot use cloud messaging services. The self-hosting capability, open source code, and air-gapped deployment make it unique in the market. The tradeoff is setup complexity and a less polished experience than commercial tools. If data sovereignty is non-negotiable, Mattermost is the answer.
Price History
Mattermost removed public pricing, all paid plans now Contact Sales
Detected by automated price watch. Professional was $10/user/mo, now requires contacting sales.