X (Twitter) phone verification: codes, rejected numbers and fixes

X (formerly Twitter) leans on phone verification to slow down spam and bot accounts. That means real users get asked too: at sign-up, after a password reset, or when the account is temporarily locked. This guide explains each case and what to do when the SMS step fails.

When X asks for a phone number

• At sign-up, if you choose phone instead of email, or if X's risk checks want an extra step.
• When an account is locked for "unusual activity" and X asks you to confirm a number to unlock it.
• When you turn on SMS two-factor authentication (an option for X Premium subscribers; others can use an authenticator app or security key).

If the code doesn't arrive

• Check that the country code is right and that you didn't type the leading 0 of a national number.
• Wait about a minute before tapping resend; repeated requests can trigger a temporary limit.
• If nothing arrives after two tries, the number is likely being filtered. Switch to a different number instead of retrying the same one.

"This phone number can't be used"

X refuses numbers that are already on too many accounts, numbers flagged in the past, and many VoIP ranges. A fresh mobile number usually works. With Noir SMS, if X still rejects the number or no SMS arrives within 20 minutes, the charge goes back to your balance automatically, and you can cancel manually after 2 minutes.

After you're verified

• Add an email you keep under Settings > Your account > Account information.
• Turn on two-factor authentication with an authenticator app instead of SMS.
• Save your backup code somewhere safe; it's the fastest way back in if you lose your second factor.