Signal: The Best Free, Non-Ad-Supported Secure Messaging

Signal is available as an Android app and an iOS app, with companion desktop apps for Linux, macOS, and Windows. Emphasis on companion: you must still register for Signal using a mobile phone. Your Signal message history is stored locally on your devices, but you can access your old messages on desktop platforms by scanning a QR code to link your device to your computer.

(Credit: Signal/PCMag)

Signal requires a phone number to sign up. Though the service does not store or share your phone number or Source link