Two-factor authentication (2FA)

A second step at login, beyond your password, such as a code or a passkey.

Two-factor authentication requires something besides your password to log in, such as a code from an authenticator app, a passkey or a hardware security key.

It protects accounts like exchanges and email. SMS codes are the weakest form because of SIM swaps. Passkeys and security keys are the strongest because they can't be phished.