Delta Chat The European alternative to WhatsApp / Signal
Open Source SubmittedOpen-source messenger using the email protocol from Germany
About Delta Chat
Delta Chat is an open-source messenger built by merlinux GmbH in Freiburg, Germany. Instead of operating a dedicated server, the app uses the email protocol as its transport layer. Messages route through so-called Chatmail relays or any standard email server, no account, phone number or central provider is required. Since version 2 (July 2025), end-to-end encryption based on OpenPGP and Autocrypt is enabled by default.
Highlights
- ✓ Email protocol as transport, no dedicated account or phone number
- ✓ End-to-end encryption by default (OpenPGP/Autocrypt) since version 2
- ✓ Federated: works with any email server or Chatmail relay
- ✓ Cross-platform (Android, iOS, Linux, macOS, Windows)
- ✓ Open source under GPLv3
Why European?
- → Developed by merlinux GmbH in Freiburg under EU data protection law
- → Decentralized and federated via open email standards, no central provider
- → Co-funded by the EU NEXTLEAP project, Sovereign Tech Fund and Open Technology Fund
- → Open source: fully auditable
Pricing
Free (open source)
Frequently asked questions about Delta Chat
What is Delta Chat and what is it used for? +
Delta Chat is an open-source messenger based on the email protocol, developed by Merlinux GmbH in Freiburg (Germany). The app looks and works like a conventional messenger but uses existing email accounts for message transport in the background. Messages are protected with Autocrypt (end-to-end encryption). Delta Chat is available for Android, iOS, and desktop (Linux, Windows, macOS).
Does Delta Chat run on European infrastructure? +
Delta Chat uses the user's existing email infrastructure. There is no central server. Messages travel through the email provider of each user (for example, mailbox.org, Posteo, Tuta). This means users themselves determine where data is processed. Merlinux GmbH as the development company is based in Freiburg (Germany). The software is open source under the GPL-3.0 license.
What distinguishes Delta Chat from Signal? +
Delta Chat does not require a phone number or central server, instead using existing email accounts. Signal requires a phone number and uses central AWS servers. Delta Chat is interoperable with any email account worldwide. Signal offers a more polished messaging experience with better group chat and call functionality. Both are open source and offer end-to-end encryption.
Try Delta Chat
Open-source messenger using the email protocol from Germany
Visit Delta Chat Website → 
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Entry verified on 08.05.2026