Delta Chat

Delta Chat is an end-to-end encrypted messenger built on email standards, from merlinux GmbH in Freiburg, and there is no central Delta Chat server: messages travel over chatmail relays or over any email server the user picks. With Delta Chat the operator of the server is whoever the user chose, which can be a public relay, a provider the user already trusts, or the user.

Delta Chat is free and open source: the core is published under MPL-2.0, the Android app under GPL-3.0 and the chatmail relay software under MIT, so an organisation can read the client core and the relay code and run a relay of its own. Delta Chat supports multiple profiles and multiple devices.

The caveat with Delta Chat is the default setting. The default Delta Chat relay, nine.testrun.org, is run by testrun UG i.G., also in Freiburg, which is a different company from merlinux, and the relay's privacy policy does not name the hosting provider underneath it. A Delta Chat user who accepts the default is therefore relying on a second company and an unnamed hoster, and one who picks another relay should check who runs that one instead.

What Delta Chat does well

• No central Delta Chat server; chatmail relays or any email server carry the messages
• Free and open source, with the core under MPL-2.0 and the Android app under GPL-3.0
• Relay software under MIT, so an organisation can run its own relay
• Multiple profiles and multiple devices
• Made by merlinux GmbH in Freiburg, under German jurisdiction

Where Delta Chat falls short

• The default relay is run by testrun UG i.G., a different company from merlinux
• The hosting provider behind the default relay nine.testrun.org is not named
• Where messages pass depends on the relay chosen, so the data-location answer varies per user
• Vetting a relay is left to the user

Standout feature. An operator you pick: Delta Chat has no central server, so the relay carrying a conversation is run by whoever the user chose, the user included.