Universal 2nd Factor (U2F) is an open authentication standard originally developed by Google, Yubico, and NXP Semiconductors that strengthens and simplifies two-factor authentication using a specialized NFC, Bluetooth, or a USB security device such as the Yubikey or Ledger Wallet.
A U2F security key can be used as an additional method of strong, easy to use, and a highly private second factor of verification before performing logins, password changes, API key creation, account modifications, changes to sensitive security measures, and confirming withdrawals.