Mattermost

What Mattermost does

Mattermost is a team chat server that looks and works much like Slack: teams contain public and private channels, conversations can branch into threads, and people can message each other directly or in small groups. On top of chat it ships voice calls with screen sharing, Playbooks for repeatable processes such as incident response, and a plugin system with integrations for Jira, GitHub, GitLab, Zoom and many other tools. The company positions it for technical and operations teams, including DevOps groups, IT service desks and organizations in regulated sectors.

The whole product is written in Go and React and runs as a single Linux binary backed by PostgreSQL. A new compiled release comes out every month.

Editions and licensing

Mattermost is open core, and the edition you run matters more than with most tools in this category.

• Team Edition is the open source build. Mattermost describes it as intended for small teams, hobbyists or personal use below 250 activated users where single sign-on is not needed, and does not recommend it for government or sensitive commercial workloads. GitLab SSO is being removed from it.
• Mattermost Entry is a free self-hosted edition that includes the Enterprise Advanced feature set with limits: only the most recent 10,000 channel messages across the server can be viewed or searched, calls are capped at 40 minutes, and boards, playbook runs, AI queries and push notifications have monthly caps (some of these limits take effect in a future release). It has no compliance features or high availability and is meant for teams under 50 users.
• Professional, Enterprise and Enterprise Advanced are paid and add SSO with SAML, OpenID Connect or Entra ID, AD/LDAP sync, guest accounts, compliance exports, data retention, clustering and support.

The source is available under AGPL-3.0 or a commercial license; official binaries are MIT. The documentation lists Slack migration as available on Entry and the paid plans.

Self-hosting Mattermost

Install options include Docker, a tarball, the Omnibus package for Ubuntu, and a Kubernetes operator with Helm. Supported server systems are Ubuntu 22.04+, Debian Bookworm+, RHEL 9+ and compatible distributions, and PostgreSQL 15 or later is required; MySQL support is being deprecated. The sizing guide suggests 1 vCPU and 2 GB of RAM for up to 1,000 users and 2 vCPUs with 4 GB for up to 2,000. Files can go on local disk, NFS or any S3-compatible storage.

Multi-server high availability, Elasticsearch-based search and performance monitoring are Enterprise features. Database search has documented gaps, such as not finding email addresses or terms with dashes.

Hosted version

Mattermost Cloud comes in Dedicated and Shared variants and is sold as an annual subscription through sales, with a minimum of 100 users. Dedicated instances, logs and backups sit in AWS us-east-1 in Virginia; other regions require talking to sales or a partner. A free cloud trial is available.

Limitations

The open source edition lacks SSO, guest accounts and compliance tooling, and the free Entry edition’s 10,000-message history cap makes it unsuitable for long-lived workspaces. End-to-end encryption of messages is not part of the core product. The hosted service is US-based by default and aimed at organizations buying at least 100 seats.

Who it suits

Mattermost fits engineering and operations teams that want Slack-style chat on their own server, especially when they plan to buy a commercial license for SSO and compliance later. Small teams that need SSO or long history for free should compare Zulip, and organizations that need end-to-end encryption should look at Element or Wire. See the team chat guide for the wider comparison.