Universal 2nd Factor
Universal 2nd Factor (U2F) is an open standard that strengthens and simplifies two-factor authentication (2FA) using specialized Universal Serial Bus (USB), near-field communication (NFC), or Bluetooth Low Energy (BLE) devices based on similar security technology found in smart cards. It is superseded by the FIDO2 Project, which includes the W3C Web Authentication (WebAuthn) standard and the FIDO Alliance's Client to Authenticator Protocol 2 (CTAP2).