Signal is the messaging app that security researchers actually use. Developed by the Signal Foundation, a nonprofit created in 2018 by Moxie Marlinspike (the cryptographer behind the Signal Protocol) and Brian Acton (WhatsApp co-founder, who donated $50 million to start the foundation), Signal has become the gold standard for private communication.
The Signal Protocol — the encryption technology at Signal’s core — is so well-regarded that it’s been adopted by WhatsApp, Facebook Messenger, Skype, and Google Messages for their encrypted communications. But Signal itself goes further than any of these in protecting user privacy.
Signal collects almost no metadata. While other encrypted apps might protect message content but still collect who you talk to, when, and how often, Signal’s architecture minimizes even this information. The app doesn’t store contact lists on its servers, and its “sealed sender” feature hides who’s sending messages even from Signal’s own infrastructure.
The app supports text messaging, voice and video calls (including group calls), disappearing messages, file sharing, and group chats. It’s available on iOS, Android, Windows, macOS, and Linux. Everything is end-to-end encrypted by default, with no option to turn it off.
Signal has seen dramatic growth during moments of privacy concern. Downloads surged after WhatsApp’s controversial 2021 privacy policy update and have spiked following various government surveillance revelations. The app doesn’t disclose exact user numbers, but estimates place it at 40-70 million users globally.
Being a nonprofit means Signal doesn’t need to monetize its users. There are no ads, no tracking, and no data harvesting. The foundation runs on donations and grants. This model raises questions about long-term financial sustainability, but it also means Signal has no financial incentive to compromise on privacy — a rare thing in the messaging world.
