European alternatives to Slack
Slack is the well-known team chat based in the US. European alternatives offer secure team communication with EU/Swiss data storage or self-hosting.
Why look for an alternative?
Reasons include EU/Swiss data storage, end-to-end encryption, self-hosting and independence from a US provider.
What to look for in an alternative
- EU/EEA/Swiss data storage or self-hosting
- Team chat, channels and files
- Voice and video calls
- Encryption and roles
- DPA
The best European alternatives at a glance
Sorted by suitability as a replacement for the tool you searched. The Sovereignty Score independently rates how European and data-sovereign a provider is – so the two values can differ.
Secure, open-source team communication from Switzerland/Germany – end-to-end encrypted chat, calls and files, self-hostable.
Open-source, self-hostable collaboration platform from Germany – files, calendar, office and more.
Swiss end-to-end encrypted messenger with a zero-knowledge architecture – servers in Switzerland, usable without a phone number.
Comparison table
The top providers in detail
Wire is a secure collaboration platform by Wire Swiss GmbH (Zug, with development in Berlin) offering end-to-end encrypted chat, voice and video calls, conferences and file sharing. Both client and server code are open source; organizations can self-host Wire with the open-source server or use the hosted version, which according to the provider runs in EU data centers (Germany, Ireland) and is ISO 27001/27701 certified. With its dual Swiss/EU setup and independent security audits, Wire is a sovereign European alternative to Slack or Microsoft Teams – especially for public authorities, regulated industries and teams with high confidentiality requirements.
Strengths
- End-to-end encrypted chat, calls and files
- Client and server open source, self-hostable
- Swiss/EU setup, EU data centers, ISO 27001/27701
- Independent security audits available
Weaknesses
- Smaller integration ecosystem than Slack/Teams
- Self-hosting (Kubernetes stack) requires operational expertise
- Fewer app marketplace and automation options than large US providers
Nextcloud is the leading open-source alternative to cloud suites such as Google Workspace or Microsoft 365. Self-hosted or operated through a European provider, Nextcloud combines file sharing, calendar, contacts, video calls and office editing. Full data sovereignty is therefore central. The Community Edition (AGPLv3) is free for unlimited users – only the costs of your own server apply; Nextcloud Enterprise with support starts at around €69 per user per year (from 100 users).
Strengths
- Full data sovereignty through self-hosting
- Open source with a large app ecosystem
- Covers files, groupware and office
Weaknesses
- Self-hosting requires operation and maintenance
- Performance depends heavily on your own infrastructure
Threema is a secure messenger by Threema GmbH in Pfäffikon, Switzerland. Messages, calls and files are end-to-end encrypted; thanks to a zero-knowledge architecture and perfect forward secrecy, only the intended recipient can read the content – neither third parties nor Threema itself. The servers are located in an ISO 27001-certified data center in Zurich, and development takes place exclusively in Switzerland. The app clients are open source. For organizations, Threema Work offers a GDPR-compliant business variant, and Threema OnPrem a self-hostable solution. This makes Threema a strong fit for public authorities, regulated industries and teams with the highest privacy requirements.
Strengths
- End-to-end encryption with a zero-knowledge architecture
- Servers in Switzerland (ISO 27001), development in Switzerland
- Usable without phone number/email (data-minimising)
- Threema Work and OnPrem (self-hostable) for organizations
Weaknesses
- Only the app clients are open source; the server is proprietary
- More of a messenger than a full team collaboration hub
- Switzerland (EFTA), not an EU member state
Migration effort
| Providers | Migration effort | Fit |
|---|---|---|
| Wire | medium | 82/100 |
| Nextcloud | medium | 72/100 |
| Threema | low | 66/100 |
When switching pays off
For secure, open-source team communication (chat, calls, files), Wire is strong and self-hostable. If you already use Nextcloud, Nextcloud Talk works; for highly secure messaging, Threema Work fits.
When to stick with your current tool
If you use many Slack integrations and bots, check whether the alternative covers your key workflows.
Frequently asked questions
Is there an encrypted Slack alternative?
The Sovereignty Score is an editorial orientation aid, not legal advice. How we rate.