Signal Desktop

Signal Desktop is the computer companion to the Signal app on a phone. It is linked to an existing phone account by scanning a QR code; it is not a standalone account, and the phone is what registers the phone number.

Messages, calls and attachments use the Signal protocol, which applies end-to-end encryption so that the servers relaying a message do not hold the keys to read it. Once linked, the desktop app receives new conversations directly rather than mirroring the phone screen, so it keeps working while the phone is asleep.

It covers one-to-one and group conversations, voice and video calls, disappearing messages set per conversation, and the usual attachments and reactions. Older message history from before linking stays on the phone and is not copied across.