Mattermost
Open-source, self-hostable team chat built as a Slack alternative.
Self-hosted Open source AGPL-3.0 (with proprietary Enterprise tier) chatself-hosting
Pricing
Free (self-hosted). SaaS/Enterprise from ~$10/user/month.
Mattermost mirrors Slack’s channel-based model closely enough that migrating a team over is mostly muscle memory, with the difference that you can run it entirely on your own infrastructure.
Key features
- Slack-compatible import for message history
- Self-hosted with full data control
- Playbooks for incident response workflows
- Open-source core, paid tiers for enterprise auth/compliance
Self-hosted vs. cloud
Self-hosted Team Edition is free and covers most small-to-mid team needs. Cloud and Enterprise tiers add SSO, compliance exports, and support SLAs.
Quick start
docker run -d --name mattermost -p 8065:8065 mattermost/mattermost-team-edition
Alternatives
Zulip’s topic-threading model suits async-heavy teams better. Slack trades self-hosting for the largest app ecosystem.