Signal is a popular private chat app that allows users to communicate without needing a phone number. It offers end-to-end encryption for all messages, voice and video calls, and file transfers. Signal uses your existing contact list to connect you with friends and contacts with Signal installed. It provides a unique user identifier called a Signal PIN, which can be used to secure your account and enable you to switch devices without losing your data. This feature eliminates the need to share your phone number while ensuring secure and private communication.