A one-time password (OTP) is a temporary code that is valid for a single sign-in or transaction and expires within seconds or minutes. It is generated by an authenticator app or a hardware token, or sent by SMS or email, and usually serves as the second factor in multi-factor authentication (MFA). Codes sent by SMS are exposed to SIM swapping attacks.
Related term in this glossary: Multi-Factor Authentication (MFA)
OTP, one-time passcode, TOTP, HOTP, OTP code, SMS OTP