Signal
Signal is an open-source, end-to-end encrypted messaging application that prioritizes user privacy and security. It allows users to send text messages, voice calls, video calls, and files securely, with encryption protocols that prevent third parties, including the app's developers, from accessing the content. Developed by the non-profit Signal Foundation, it is widely regarded as a gold standard for secure communication due to its transparency and strong encryption standards.
Developers should learn and use Signal when building or recommending secure communication tools, especially in contexts requiring high privacy, such as whistleblowing, sensitive business communications, or personal data protection. It is essential for understanding modern encryption practices like the Signal Protocol, which is also used by other apps like WhatsApp, making it a key skill for cybersecurity and privacy-focused development projects.