User verification serves to ensure that the person using the FIDO2 security key is in fact who they say they are. In other words, User verification ensures that the person is the true owner of the device. In comparison to user authentication that is carried out remotely by an MFA server or service, user verification is carried out locally by the security device itself and/or by a local client application.
User verification can take various forms, such as PIN, fingerprint etc.
There are 3 options for user verification
Not Required | This value indicates that user verification is not required or is discouraged when initiating registration or authentication. |
| Preferred | This value indicates that the service prefers user verification for the operation if possible, but will not fail if user verification is not enabled. |
| Required | This value indicates that the service requires user verification for the operation and will fail the operation if user verification is not enabled or was not carried out successfully |
Note that:
When User Verification is set to No Required, this doesn’t mean that User Verification is never performed. For instance, when registering a FIDO2 security key that has PIN set, user verification might be required depending on the application.
When User Verification is Preferred, the user experience depends on whether or not a PIN is set or a fingerprint is enrolled on the user’s security key. To achieve a uniform user experience, explicitly set User Verification to either Not Required or Required according to your specific use case.
When User Verification is Required, keep in mind that registration or authentication will fail in the following cases:
the user has not set a PIN or enrolled a fingerprint on his or her security key. Some browsers will ask the user to set a PIN or enroll a fingerprint during registration, but others don’t. So, the behaviour cannot in general be relied on.
the user is using a security key that does not support user verification (for instance, a U2F key)
the user is using a browser that does not support user verification (for instance, browsers that implement CTAP1 only)