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

If the token from that page doesn't work, you can try https://signalcaptchas.org/challenge/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. Hint: Enable the option "Persist Logs" in the "Console Settings" to prevent clearing the console each time navigating to a new page.

Check the console in the developer tools for a redirect starting with signalcaptcha:// Everything after signalcaptcha:// is the captcha token (INCLUDING the signal-recaptcha-v2.6LfBXs0bAAAAAAjkDyyI1Lk5gBAUWfhI_bIyox5W.registration part).

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

signal-cli -u USERNAME register --captcha signal-recaptcha...03AG...Uonw

If you do not get any error, you can proceed with the verify command. If you get the error Invalid captcha given., try to get the captcha again (the captcha is good for a short period of time).