Signal is a free, 🏷️#open-source encrypted 🏷️#messaging-platform for text, voice, and video, stewarded by the nonprofit Signal Technology Foundation. Every message and call is end-to-end encrypted by default with the Signal Protocol, and both the apps and the server are published under the AGPL-3.0 license. It runs on Android, iOS, and desktop, carries no ads, and is funded by donations rather than data collection.
Signal traces back to TextSecure and RedPhone, two apps that Moxie Marlinspike's Whisper Systems released in 2010; under Open Whisper Systems the pair merged into Signal beginning in July 2014. In 2018 WhatsApp co-founder Brian Acton provided $50 million in initial funding to launch the Signal Foundation, and Meredith Whittaker became its president in 2022. The Signal Protocol also secures 📝WhatsApp, so Signal's distinction rests less on its cryptography than on minimal metadata collection and nonprofit independence, in contrast to 📝Telegram, whose chats are not end-to-end encrypted by default. Its users range from journalists and activists to senior government officials, a reach that surfaced in the March 2025 📝Signalgate leak.
Signal's choice to let encryption keys live on multiple devices, desktops included, has always troubled me because it widens the attack surface. I unpack that tradeoff in 📝Kibu vs. Signal, and it's why I've come to rely more on 📝Kibu for conversations that need to stay locked down.
Key Features
- End-to-end encryption by default — Messages, calls, attachments, and group chats are encrypted with the Signal Protocol, so Signal itself cannot read them.
- Disappearing messages — Per-chat timers automatically delete messages from every device after a chosen interval.
- Sealed sender — Hides who sent a message from Signal's own servers, limiting the metadata the service can observe.
- Usernames — Since 2024, people can connect through a username instead of sharing a phone number.
- Linked devices — Desktop and tablet apps link to a phone account, trading a wider key footprint for multi-device convenience.