ZeroTwo uses one CAPTCHA: a Cloudflare Turnstile check on the web sign-in page. It can appear when you sign in with an email address or a phone number, and only there. You do not meet it while chatting, and the sign-in screens in the iPhone, iPad and Android apps do not include it.
When it appears
- On the sign-in page, type a full email address, or choose Continue with phone and enter a complete phone number.
- The check appears beneath the field. Complete it.
- Select Continue. Until the check is complete, the button stays disabled.
If the form is submitted without a completed check, the page says "Please complete the captcha to continue." The check also resets after each attempt to send a link or code, so every new attempt needs a fresh check.
Continue with Google, Continue with Apple and Continue with Microsoft do not show it. They run a separate background check instead, described in What does "Unusual activity detected" mean when I sign in?.
If it will not clear
- No check on screen. It appears only once ZeroTwo accepts what you typed. Make sure the email address is complete or the phone number has all its digits.
- The check expired or failed. ZeroTwo clears it and keeps Continue disabled until you complete a new one.
- "Captcha verification failed. Please refresh and try again." When you sign in by email, this means ZeroTwo's server did not accept the check. Refresh the page and start again.
- Still stuck. Use another sign-in method. See Why does ZeroTwo say SMS sign-in is not available for my number? if phone sign-in is what blocked you.