AltF Authenticator
Why is my 2FA code not working?
A wrong device clock is the most common reason a 2FA code is rejected, because the code depends on the current time. Turn on automatic date and time, then try a fresh code. If that does not fix it, check that you are using the right account, that the secret was typed correctly, and that the service does not use non-default settings.
- Free, no sign-up
- Secrets stay in your browser
- RFC 6238 self-test built in
- Works on mobile
Check these in order
- Clock: open the Clock check tab. If your device is more than a few seconds off, turn on automatic date and time and set the correct time zone.
- Timing: type the code with time to spare. If the countdown is almost over, wait for the next one.
- Account: many apps hold several entries with similar names. Make sure the issuer and account match the site you are signing in to.
- Secret: if you typed the secret by hand, a single wrong character gives wrong codes. Add it again from the QR code.
- Settings: some services use 8 digits, a 60-second period or SHA-256. Check the otpauth:// link or the service's help page.
- Old enrolment: if you turned 2FA off and on again, the old secret no longer works. Remove the old entry and add the new one.
Why the clock matters so much
Your app and the server each divide the current time into 30-second steps and make a code for the current step. Most servers accept one step either side, so a clock that is off by about 30 seconds or more starts producing codes that fall outside the window. Phones that have automatic time turned off, or that were restored from a backup, often drift.
Using the toolkit to find the cause
If you have the secret, add it in the Live codes tab and compare. If this page and your app show different codes, one of the clocks or the settings differ. The Verify tab tells you which time step a code matches, which turns into a drift figure you can act on.
Still locked out?
Use one of your backup codes, or another method you enrolled. If you have none, follow the service's account recovery process; no outside tool can make valid codes without the secret.
Why is my 2FA code not working?: questions and answers
Does Google Authenticator have a time sync option?
The Android app has had a Time correction for codes option in settings on some versions. On any phone, turning on automatic date and time in the system settings is the reliable fix.
My clock is right but codes still fail. Why?
Check the account and the settings. A secret entered with a typo, or a service that uses 8 digits or a 60-second period, gives codes that look valid but never match.
Does the clock check send my secret?
No. It makes one request to AltFTool's server for the current time. It carries no secret, code or account.
Can a time zone change break codes?
Not by itself. Codes use Unix time, which ignores time zones. They break when the actual clock is wrong, for example when the time was set by hand.
Authenticator tools and 2FA guides
Guides
AltFTool never receives your secrets or codes. The only network request any tab makes is the clock check, which asks AltFTool's server for the time and carries nothing else.