Signal

Signal is a messaging app built entirely around the idea that private conversations should be the default, not a premium feature. Developed by the Signal Foundation—a 501(c)(3) non-profit—it provides end-to-end encrypted text messaging, voice calls, video calls, group chats, and file sharing across iOS, Android, and desktop. The encryption protocol Signal uses (the Signal Protocol) is so well-designed that WhatsApp, Google Messages, and Facebook Messenger adopted it for their own encrypted modes. The difference is that Signal doesn't collect metadata, doesn't serve ads, doesn't build user profiles, and can't read your messages even if served with a court order. The organization has publicly demonstrated this: when subpoenaed by a grand jury, Signal could only produce the date an account was created and the date it last connected. No message content, no contact lists, no group memberships. The macOS desktop app syncs with your phone via an encrypted link. Messages are stored locally on your devices—not on Signal's servers. The desktop client supports everything the mobile app does: individual and group messages, voice messages, disappearing messages, reactions, stickers, stories, polls, pinned messages, and username-based contact (so you can message people without sharing your phone number). It's an Electron app with proper macOS notifications, system dark mode support, and keyboard shortcuts. For developers and privacy-conscious professionals, Signal is the messaging app that respects you enough to not monetize your conversations.