# Mattermost

> Mattermost is a mature open core Slack alternative (Go and React, PostgreSQL). Two free routes: the MIT-licensed Team Edition, aimed at teams under 250 users and losing SSO since 2025; or the Enterprise build run free as "Entry", which caps viewable history at 10,000 channel messages and suits under 50 users. Compliance, high availability and support are paid. Up to 1,000 users need about 1 vCPU and 2 GB RAM. Desktop and mobile apps exist. The server runs on Linux or in Docker, not natively on Windows.

- Repository: https://github.com/mattermost/mattermost
- Official docs: https://docs.mattermost.com/
- Checked: 2026-10-15

## What it replaces
- Slack: Channels and direct messages, Threaded conversations, Voice and video huddles, Integrations, Search and message history (partial). Covers core Slack work; free editions have user, history (Entry) and SSO (Team Edition) limits. Feature parity not checked.

## Facts, with sources

| Question | Status | Answer | Source | Checked |
|---|---|---|---|---|
| Runs on my machine? | Confirmed | Self-hosted server (Docker, Linux package or tarball) or Mattermost Cloud | https://github.com/mattermost/mattermost#readme | 2026-10-15 |
| Code licence | Partial | Source under AGPL-3.0 (or commercial licence); Mattermost-built binaries under MIT; admin tools and config under Apache-2.0 | https://github.com/mattermost/mattermost/blob/master/LICENSE.txt | 2026-10-15 |
| Model weights licence | Confirmed | No separate model weights | https://github.com/mattermost/mattermost#readme | 2026-10-15 |
| Commercial use | Partial | Yes; Team Edition (MIT binary) is advised for under 250 users, Entry has history and other limits; AGPL applies to modified builds; trademark needs approval | https://docs.mattermost.com/product-overview/editions-and-offerings.html | 2026-10-15 |
| Paid services needed? | Partial | None required; paid subscriptions add SSO (beyond Entry), compliance, high availability, full history and support | https://docs.mattermost.com/product-overview/editions-and-offerings.html | 2026-10-15 |
| Hardware | Confirmed | 1 vCPU and 2 GB RAM for up to 1,000 users; 2 vCPU and 4 GB RAM for 1,000-2,000; PostgreSQL 14+ | https://docs.mattermost.com/deployment-guide/software-hardware-requirements.html | 2026-10-15 |
| Operating systems | Confirmed | Server on Linux (Ubuntu, Debian, RHEL 9) or Docker; desktop apps for Windows 11+, macOS 14+, Ubuntu; iOS and Android apps | https://docs.mattermost.com/deployment-guide/software-hardware-requirements.html | 2026-10-15 |
| Setup effort | Confirmed | Medium; Docker Compose, Ubuntu package, tarball or Kubernetes, plus PostgreSQL | https://github.com/mattermost/mattermost#readme | 2026-10-15 |

GitHub: 39346 stars, 9052 forks, last push 2026-10-16, archived: no.
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Source: RepoQuarry (https://repoquarry.dev/projects/mattermost). Data licence: CC BY 4.0. Quotes are from project documentation and belong to their authors.