Mobile: Signal

Open-Whisper-Systems

Signal is a mobile app developed by Open Whisper Systems. The app provides instant messaging, as well as voice and video calling. All communications are end-to-end encrypted. Signal is free and open source, enabling anyone to verify its security by auditing the code. The development team is supported by community donations and grants. There are no advertisements, and it doesn’t cost anything to use.

OS: Android, iOS.

Wire

wire

Wire is an app developed by WIRE SWISS GmbH. The Wire app allows users to exchange end-to-end encrypted instant messages, as well as make voice and video calls. Wire is free and open source, enabling anyone to verify its security by auditing the code. The development team is backed by Iconical and they will monetize in the future with premium features/services.

OS: Android, iOS, macOS, Windows, Linux, Web

Desktop: Ricochet

Ricochet

Ricochet uses the Tor network to reach your contacts without relying on messaging servers. It creates a hidden service, which is used to rendezvous with your contacts without revealing your location or IP address. Instead of a username, you get a unique address that looks like ricochet:rs7ce36jsj24ogfw. Other Ricochet users can use this address to send a contact request – asking to be added to your contacts list.

OS: Windows, Mac, Linux.