TOTP code generator

When your authenticator app is not at hand: a lost, broken or new phone, or a shared account whose key you keep in a password manager. Developers also use it to test their own two-factor setup.

When you turn on two-factor authentication, the service shows a QR code and usually a "Can't scan it?" link with the key as text, such as JBSW Y3DP EHPK 3PXP. Password managers like 1Password and Bitwarden show the key in the item's one time password field, and a Google Authenticator export contains it too. You can paste the key or scan the QR code here.

Codes are calculated in your browser with the open source otpauth library. The key is never sent to a server or saved, and it is gone when you close the tab. To check, turn off your internet after the page loads: codes keep coming. Still, treat the key like a password and only use it on a device you trust.

If you have the secret key, get a code here, sign in, and set up two-factor authentication again on your new phone from the service's security settings. That gives you a new key, so the lost phone stops working for that account. Without the key, use the recovery codes the service gave you when you turned two-factor on.

Codes depend on the time, so first make sure your device sets its clock automatically. If the countdown is almost over, wait for the next code. If it still fails, check the code settings: a few services use SHA256, 8 digits or 60 seconds.

In Google Authenticator open Transfer accounts, then Export accounts, and scan the QR code with the camera here. Every time based account in the export is listed and you pick the one you need.