Signal
Visit WebsiteSignal is a messaging app developed by Signal Messenger LLC and supported by a 501(c)(3) nonprofit. It has instant messaging, voice, and video calling. Everything is end-to-end encrypted unless you choose to send as SMS.
- End-to-end encrypted messages and calls
- Independently audited
- Usernames option (communicate without sharing phone numbers)
- Phone number required to start
- Free and open-source
Signal’s protocol is used by other apps including WhatsApp.