Slack vs. Mattermost
Side by side, with sources. Checked Oct 3, 2026.
Slack
Paid plans
Mattermost
Open sourcePrice
Free plan with 90 days of history and up to 10 apps. Pro is US$8.75 and Business+ US$18 per user per month billed monthly (US list prices).from $8.75/user/monthSource: salesforce.com
Free self-hosted Team Edition (open source) and Entry (free, limited). Professional and Enterprise are annual per-seat plans with no public price.Source: mattermost.com
Pricing model
Paid plans · Free plan available
Open source · Free plan available
License
ProprietaryA proprietary cloud service under Slack’s Main Services Agreement.
Open core · AGPL-3.0-onlyMattermost-built binaries are MIT, the source is AGPL-3.0 or commercial, and enterprise features are commercial. The desktop app is Apache-2.0.
Works on
- ✓ Windows
- ✓ Mac
- ✓ Linux
- ✓ iPhone & iPad
- ✓ Android
- ✓ Web browser
- – Your own server
- ✓ Windows
- ✓ Mac
- ✓ Linux
- ✓ iPhone & iPad
- ✓ Android
- ✓ Web browser
- ✓ Your own server
Where your data lives
In Slack’s cloud, stored in the US unless your organisation sets up data residency (Business+ or higher).
On the server your organisation runs, on its own premises or cloud.
Getting started
—
Difficulty: Advanced There is no public sign-up: either you join a server your organisation already runs, or someone has to run a Linux server for you.
Hosted version
—
NoneThe only hosted option, Mattermost Cloud Enterprise, is sold to enterprises through sales.
Our take
A solid choice when your organisation can run its own server and wants chat data in-house. Small teams without IT help will find it harder to start.
Best for
Organisations with IT support
Companies and public bodies that need chat on their own infrastructure, with control over retention and access.
Check first
Who will run the server
There is no public sign-up for small teams, and paid tiers are sold through sales with no public prices.