Backup codes let you complete two-factor sign-in when you cannot receive the normal verification code. Each code can be used once.
Keep them somewhere separate
- A trusted password manager is a good choice.
- A printed copy in a secure place can also work.
- Do not keep the only copy in the same email account you are trying to access.
- Do not send them to anyone.
You can generate a new set from two-factor settings. Doing that invalidates the old codes.
Tip: Treat backup codes like passwords. Anyone with one may be able to pass the second sign-in step.