A FIDO U2F Security Key is an open authentication standard that strengthens and simplifies 2FA using specialized USB or NFC devices based on similar security technology found in smart cards. U2F Security Keys are currently only supported by Google Chrome since version 38 and Opera since version 40.
If you choose the “FIDO U2F Security Key” option, the next screen will prompt the user to insert their security key into the USB port on their computer. This will register the device with their ID.me account and the 2-factor authentication enrollment process will be complete.
If the user chose to add the additional layer of security with 2FA, they will see a screen confirming that they’ve completed the enrollment process.