Signal is a messaging app that provides secure, encrypted communication through the use of the open source Signal Protocol. It is fast and reliable, even on slow networks, and is optimized to operate in constrained environments. There are no ads or trackers on the app, and it is supported by users. With Signal, you can use your existing phone number and address book to communicate with your friends and family, and make HD voice and video calls. It also has a dark theme option and allows you to customize alerts or disable noises completely. The app has image editing features and a text tool for outgoing photos.