Mattermost is controlled from a country outside the EU and lacks confirmed EU data storage: processing effectively takes place in a third country. That makes the tool unsuitable for sensitive personal data without additional safeguards. For non-personal data (drafts, public material) it is usually fine.
Swedish team chat with channels, direct messages as well as voice and video calls, running on Webbfabriken's own servers in Stockholm. Drawback: small vendor and a young service without a large ecosystem of integrations.
All data is stored in Stockholm, built and run by a Swedish company
Free for now, with core features such as channels, video and file sharing
Small vendor: long-term future and pricing model unclear (free now, paid tiers may come)
Best for: Small Swedish teams that want all chat data to stay in Sweden without American cloud.
EU/EEACollaborationFreemiumEU data storage ✓ISO 27001
End-to-end encrypted messaging and collaboration app with servers in Germany and Ireland. Drawback: the company is based in Switzerland (outside the EU/EEA) and the service is more messaging than full collaboration tool.
Strong end-to-end encryption for everything including calls
Data stored in the EU (Germany/Ireland), GDPR- and ISO 27001-aligned
The company is headquartered in Switzerland, i.e. outside the EU/EEA
Best for: Security-conscious teams that prioritize strong encryption for messages and calls.
No, Mattermost has no confirmed EU data storage: data is processed in a third country.
Is Mattermost covered by the CLOUD Act?
The vendor is based outside the EU. US companies are covered by the CLOUD Act regardless of server location; see the tool page for details.
What is needed to use Mattermost in a GDPR-safe way?
Sign a data processing agreement (DPA) if the tool processes personal data on your behalf, minimise the personal data you feed in, and check the vendor's sub-processors. See our DPA guide for the steps.
Our assessment is based on verified data about vendor, storage and certifications (2026). GDPR compliance also depends on how you use the tool. This is guidance, not legal advice. See How we review.
