Privacy controversies aside, WhatsApp is one of the most popular and useful apps in the world. The app supports the same rich instant messaging experience you’d get in iMessage, Facebook Messenger, and Telegram, and it handles voice and video calls. Unlike Facebook Messenger, it comes with the same strong end-to-end encryption as iMessage and Signal. And unlike iMessage, it works on iPhone and Android. It is no wonder that Facebook paid nearly $20 billion many years ago on an app that bridges chat communications between platforms securely.