Registration with captcha

Sometimes the Signal server requires a captcha token for registering a new account. If your IP address is not deemed trustworthy enough, the registration fails with a captcha required error (Captcha invalid or required for verification).

To get the token, go to https://signalcaptchas.org/registration/generate.html

After filling the captcha, the site doesn't show the token but redirects to a signalcaptcha:// url that contains the token. On mobile devices that url is handled by the apps. To see the URL you can open the browser developer tools (F12) before completing the captcha.

Check the console in the developer tools for a redirect starting with signalcaptcha:// Everything after signalcaptcha:// is the captcha token.

Then execute the register command again with the --captcha argument (https://github.com/AsamK/signal-cli/blob/master/man/signal-cli.1.adoc#register)