Using Signal Without a Smartphone

This is a quick guide on how to set up Signal Desktop without using the official Signal app, but by using the unofficial CLI tool signal-cli.

Installation

sudo pacman -S signal-desktop
yay -S signal-cli

Install Java Standard Edition, as well as Signal for Desktop. Also download the pre-compiled binary for signal-cli.

Extract the signal-cli archive and cd into the bin folder.

For the following commands, replace signal-cli with signal-cli.bat.

Make sure to write you phone number with its country code (like +32 for Belgium).

Open https://signalcaptchas.org/registration/generate.html and solve the captcha. Right-click on “Open Signal” and press “Copy Link”.

signal-cli -u <phone-number> register --captcha "<copied-captcha>"

Verify the registration with the code you received via SMS. If you set up a Signal PIN before, enter that too:

signal-cli -u <phone-number> verify <code> --pin <signal-pin>

Take a cropped screenshot of the QR code shown in Signal Desktop and decode with zbarimg:

maim -s /tmp/qr.png && zbarimg /tmp/qr.png

Alternatively you could use one of the many QR-Code Decoder websites.

Add the device with the decoded QR-Code:

signal-cli -u <phone-number> addDevice --uri "<decoded-qr>"

If you want you can also specify your Name and profile picture:

signal-cli -u <phone-number> updateProfile --name "<name>" --avatar <path/to/pic>

In my case my recent chats did not appear in the desktop app, until I queried the server for new messages with:

signal-cli -u <phone-number> receive