Two-step sign-in

☰ menu → Security (or g then u).

• Code by email: press Turn on with email. Each sign-in emails you a 6-digit code.
• Authenticator app (recommended): press Set up an authenticator app, scan the QR code with Google Authenticator, Microsoft Authenticator, 1Password or Authy, then enter the code and your password.
• Recovery codes: shown once when you set up the app. Each works once instead of the app. Save them somewhere safe; Make new recovery codes replaces them.
• Trusted devices: when signing in you can trust the browser so it skips the code for a while. Forget trusted devices here.
• Move to a new phone: set up the app again on the new phone.

If the page says Required for administrators, two-step sign-in cannot be turned off for your account.