We moved our 12-person team from Slack to Mattermost for 30 days. Channels, threads, integrations, bots β everything tested head-to-head.
If your team needs channels, threads, file sharing, and webhooks without paying $150/user/year β Mattermost is a serious Slack alternative.
We migrated a 12-person remote team from Slack Pro to self-hosted Mattermost for 30 days. We tested three core workflows: daily team communication (channels, threads, mentions, DMs), DevOps integrations (GitHub, GitLab, Jira, CI/CD bots), and async collaboration (file sharing, search, playbooks). Every friction point was documented.
Full data ownership (self-hosted), unlimited message history on the free plan, DevOps-native integrations (GitLab, Jenkins, Jira built-in), powerful webhooks and Slash commands, customizable with plugins, and no per-user pricing wall. Your data stays on your server β GDPR compliance is built-in.
Huddles (voice/video calls) are smoother, the app marketplace is 10x larger, Slack Connect for cross-org communication, polished mobile experience, Workflow Builder for no-code automations, and the "everyone already uses it" network effect. Slack's search across channels is also faster and more intuitive.
Scored 0β10 based on 30 days of real use with a 12-person team.
Feature-by-feature breakdown after 30 days of real-world use.
| Feature | Mattermost (Free) | Slack ($150/user/yr) |
|---|---|---|
| π° Price (50 users) | $0 (self-hosted) | $7,500/yr |
| π¬ Message History | Unlimited (all plans) | 90 days (free plan) |
| ποΈ Voice/Video Calls | Plugin (basic) | Huddles (built-in) |
| π Webhooks | Incoming + Outgoing | Incoming + Outgoing |
| 𧩠App Marketplace | ~100 plugins | 2,600+ apps |
| π Self-Hosted | Full control | SaaS only |
| π LDAP/SSO/SAML | Free plan included | Enterprise plan only |
| π€ Bot Framework | Full SDK + API | Bolt SDK |
| π Cross-Org Chat | Not supported | Slack Connect |
| π± Mobile Apps | iOS + Android | iOS + Android (better) |
| π Compliance Export | Built-in | Enterprise Grid only |
| π Data Ownership | 100% on your server | Slack's servers |
Based on 30 days with a real 12-person team.
Honest answer based on what we saw in 30 days of use.
Step-by-step from our actual migration experience.
Fastest path: Docker Compose. Run docker compose up -d with the official Mattermost Docker repo and you'll have a production server in under 10 minutes. Alternatively, use DigitalOcean's 1-click Mattermost droplet (get $200 free credit) ($6/mo for a small team).
Mattermost has a built-in Slack Import tool. In Slack, go to Workspace Settings β Import/Export β Export. Download the ZIP. In Mattermost, go to System Console β Import β Slack Import. All channels, messages, and users are preserved. File attachments need a separate migration script (documented in MM docs).
Install the plugins your team needs: GitHub/GitLab (PR notifications, issue tracking), Jira (ticket updates), Jenkins (CI/CD alerts), Zoom/Jitsi (video calls). All available from the Plugin Marketplace inside Mattermost's System Console.
Send invite links, set up SSO (LDAP/SAML if you have it), and create your channel structure. Pro tip: mirror your existing Slack channel layout exactly β this reduces the "where do I post this?" confusion during transition. Expect 1β2 weeks of adjustment before everyone feels comfortable.
Real questions from teams considering the switch.
Other tools we've tested in 30-day audits.
If you're paying $7,500/year for 50 Slack seats and your team is technical enough to run Docker β you're overpaying. Mattermost gives you unlimited users, unlimited history, and full data ownership at $0. The 25% gap is mainly UX polish and the app marketplace. Stop renting your communication.
Build Your Free Productivity Stack β