# User Verification User verification may be instigated through various authorization gesture modalities: a touch plus PIN code, password entry, or biometric recognition (presenting a fingerprint). The intent is to be able to distinguish individual users. Eligible authenticators are filtered and only capable of satisfying this requirement will interact with the user. Possible user verification values are: * `required`: this value indicates that the application requires user verification for the operation and will fail the operation if the response does not have the `UV` flag set. * `preferred`: this value indicates that the application prefers user verification for the operation if possible, but will not fail the operation if the response does not have the `UV` flag set. * `discouraged`: this value indicates that the application does not want user verification employed during the operation (e.g.,in the interest of minimizing disruption to the user interaction flow). Public constants are provided by `AuthenticatorSelectionCriteria`. * `AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_REQUIRED` * `AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_PREFERRED` * `AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_DISCOURAGED` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://webauthn-doc.spomky-labs.com/v4.8/webauthn-in-a-nutshell/user-verification.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.