Signal is the most scalable encryption tool.

Threema is an encrypted instant messaging application for iOS, Android and Windows Phone.

Zulip is a chat and collaborative software.

Wire is a cross-platform, encrypted instant messaging client created by Wire Swiss. It is available for iOS, Android, Linux, Windows, macOS and Web browser cl…

Sicher is a freeware instant messaging application for iOS, Android, and Windows Phone. Sicher allows users to exchange end-to-end encrypted text messages, me…