Head-to-head · Collaboration
Slack vs Mattermost
Which one to pick in 2026 — comparing 🇺🇸 Slack with the European alternative 🇪🇺 Mattermost on the things that actually decide who can read your data.
🇺🇸 Slackvs🇪🇺 Mattermost
Verdict
Who has stronger privacy guarantees by law?
Mattermost — GDPR-native and outside the US CLOUD Act / FISA 702 reach.
Which one encrypts your data end-to-end by default?
Neither ships full E2E by default — check the table for nuance.
Which one tracks you for ads?
Neither monetises through ad tracking.
Which one is open source?
Mattermost is open source. Slack is proprietary.
Side-by-side
Slack vs Mattermost — full comparison
Criteria
🇪🇺 Mattermost
🇺🇸 Slack
Headquarters
EU self-host
San Francisco, USA
Jurisdiction
USA (open-source, self-hostable in EU)
USA
Data location
EU se self-hosted
US (EU residency paid tier)
GDPR-native
Yes
No
CLOUD Act / FISA exposed
No
Yes
Ad tracking
No
No
End-to-end encryption
No
No
Open source
Yes
No
Ownership
Mattermost Inc.
Salesforce
Founded
2016
2013
Make the switch
Try Mattermost instead of Slack
Mensagens de equipa open-source
Other European alternatives to Slack