# Mattermost — Open Source Slack Alternative for Team Collaboration

> Mattermost is an open-source messaging platform for secure team collaboration. Channels, threads, voice/video calls, playbooks, and integrations — self-hosted Slack alternative.

## Install

Save the content below to `.claude/skills/` or append to your `CLAUDE.md`:

## Quick Use

```bash
docker run -d --name mattermost -p 8065:8065 
  -v mattermost-data:/mattermost/data 
  -v mattermost-config:/mattermost/config 
  mattermost/mattermost-team-edition:latest
```

Open `http://localhost:8065` — create your first team and start collaborating.

## Intro

**Mattermost** is an open-source platform for secure team collaboration across the entire software development lifecycle. It provides Slack-like messaging with channels, threads, and direct messages, plus voice/video calls, playbooks for incident response, and deep integrations with DevOps tools — all self-hosted for complete data control.

With 36.1K+ GitHub stars, Mattermost is the leading open-source Slack alternative, trusted by organizations from startups to defense departments that require data sovereignty and security compliance.

## What Mattermost Does

- **Messaging**: Channels (public/private), direct messages, group messages, threads
- **Voice & Video**: Built-in voice and video calls with screen sharing
- **Playbooks**: Structured workflows for incident response, onboarding, and release processes
- **File Sharing**: Drag-and-drop file uploads with preview and search
- **Integrations**: 200+ integrations via webhooks, slash commands, and plugins
- **Search**: Full-text search across all messages, files, and channels
- **Compliance**: Message retention, compliance exports, eDiscovery, and audit logs
- **Mobile**: Native iOS and Android apps with push notifications
- **SSO**: SAML, OAuth 2.0, LDAP/AD, and GitLab authentication

## Architecture

```
┌──────────────┐     ┌──────────────┐     ┌──────────────┐
│ Web / Desktop│────▶│  Mattermost  │────▶│  PostgreSQL  │
│ / Mobile App │     │  Server (Go) │     │  (Data)      │
└──────────────┘     └──────┬───────┘     └──────────────┘
                            │
              ┌─────────────┼─────────────┐
              │             │             │
       ┌──────┴──┐   ┌─────┴───┐   ┌─────┴───┐
       │  MinIO  │   │ Elastic │   │  SMTP   │
       │ (Files) │   │ (Search)│   │ (Email) │
       └─────────┘   └─────────┘   └─────────┘
```

## Self-Hosting

### Docker Compose

```yaml
services:
  mattermost:
    image: mattermost/mattermost-team-edition:latest
    ports:
      - "8065:8065"
    environment:
      MM_SQLSETTINGS_DRIVERNAME: postgres
      MM_SQLSETTINGS_DATASOURCE: postgres://mmuser:mmpass@db:5432/mattermost?sslmode=disable
      MM_SERVICESETTINGS_SITEURL: http://localhost:8065
    depends_on:
      - db
    volumes:
      - mm-config:/mattermost/config
      - mm-data:/mattermost/data
      - mm-logs:/mattermost/logs
      - mm-plugins:/mattermost/plugins

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: mmuser
      POSTGRES_PASSWORD: mmpass
      POSTGRES_DB: mattermost
    volumes:
      - pg-data:/var/lib/postgresql/data

volumes:
  mm-config:
  mm-data:
  mm-logs:
  mm-plugins:
  pg-data:
```

## Key Features

### Channels & Organization

```
Team: Engineering
├── #general — Team-wide announcements
├── #frontend — Frontend discussions
├── #backend — Backend discussions
├── #incidents — Active incident coordination
├── #standup — Daily standups (bot-assisted)
└── Private: #leadership — Management only
```

### Playbooks (Workflows)

Pre-built workflows for repeatable processes:

```
Incident Response Playbook:
  1. Create incident channel (auto)
  2. Assign commander and communications lead
  3. Checklist: Assess severity, notify stakeholders
  4. Status updates every 30 min (reminder bot)
  5. Retrospective template (post-incident)
  6. Archive and timeline export

Release Playbook:
  1. Create release channel
  2. Feature freeze checklist
  3. QA sign-off tasks
  4. Deploy steps with verification
  5. Rollback procedures
  6. Post-release monitoring
```

### Integrations

```
DevOps:
├── GitHub / GitLab — PR notifications, issue updates
├── Jira — Ticket creation from messages
├── Jenkins / CircleCI — Build notifications
├── PagerDuty — Incident alerts in channels
└── Grafana / Prometheus — Alert forwarding

Productivity:
├── Zoom / Jitsi — Video call integration
├── Google Calendar — Meeting reminders
├── Trello / Asana — Task management
├── Confluence — Doc link previews
└── Custom Webhooks — Any service
```

### Slash Commands

```
/jira create [summary] — Create Jira ticket
/github subscribe owner/repo — Get PR/issue notifications
/zoom start — Start a Zoom meeting
/poll "Question" "Option 1" "Option 2" — Create a poll
/standup — Post daily standup update
```

### Bot & API

```bash
# Post a message via webhook
curl -X POST http://localhost:8065/hooks/your-webhook-id 
  -H "Content-Type: application/json" 
  -d '{"text": "Build #123 passed ✅", "channel": "ci-notifications"}'

# REST API
curl http://localhost:8065/api/v4/users/me 
  -H "Authorization: Bearer YOUR_TOKEN"
```

## Mattermost vs Alternatives

| Feature | Mattermost | Slack | Microsoft Teams | Rocket.Chat |
|---------|-----------|-------|-----------------|-------------|
| Open Source | Yes | No | No | Yes |
| Self-hosted | Yes | No | Hybrid | Yes |
| Voice/Video | Built-in | Huddles | Built-in | Built-in |
| Playbooks | Built-in | Workflows (paid) | No | No |
| Compliance | Export/eDiscovery | Enterprise | Enterprise | Basic |
| Mobile | iOS + Android | iOS + Android | iOS + Android | iOS + Android |
| SSO | SAML/LDAP/OAuth | Enterprise | Azure AD | SAML/LDAP |
| Pricing | Free (Team) | Free + $8.75/user | $4/user | Free + paid |

## FAQ

**Q: What's the difference between Mattermost Team Edition and Enterprise Edition?**
A: Team Edition is fully free and open source, covering core messaging, channels, file sharing, Playbooks, and integrations. Enterprise Edition adds enterprise features like high availability, compliance exports, SAML SSO, and AD/LDAP group sync.

**Q: Can I migrate from Slack?**
A: Yes. Mattermost provides a Slack import tool that supports channels, message history, users, and files. The UX and keyboard shortcuts are highly similar to Slack, keeping team switching costs low.

**Q: What are the server requirements?**
A: Up to 50 users: 2 cores, 4 GB RAM. Up to 200 users: 4 cores, 8 GB RAM. For large-scale deployments, use a high-availability cluster configuration.

## Sources & Credits

- GitHub: [mattermost/mattermost](https://github.com/mattermost/mattermost) — 36.1K+ ⭐
- Website: [mattermost.com](https://mattermost.com)

---
Source: https://tokrepo.com/en/workflows/mattermost-open-source-slack-alternative-team-collaboration-ca6c4512
Author: AI Open Source