Signal

Signal is a scalable encryption tool to perform private calls and messaging. Make crystal-clear voice and video calls to people who live across town, or across the ocean, with no long-distance charges.
Signal messages and calls are always end-to-end encrypted and painstakingly engineered to keep your communication safe. We can't read your messages or see your calls, and no one else can either. Keep your chat history tidy with messages that you can set to disappear. Choose different disappearing message intervals for each conversation. Everyone in the thread shares the same setting. Good memories will last even if the words vanish.