# useBiometricCredentials() > This hook requires a [development build](https://docs.expo.dev/develop/development-builds/introduction/) that includes a compatible version of `@clerk/expo` and doesn't work in Expo Go. The `useBiometricCredentials()` hook provides methods to check biometric credential availability, enroll the current app installation, list and revoke credentials, and sign in returning users. ## Returns The `useBiometricCredentials()` hook returns the following methods: - [getAvailability()](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#get-availability) - [list()](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#list) - [enroll()](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#enroll) - [revoke()](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#revoke) - [signIn()](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#sign-in) ### `getAvailability()` Checks whether a biometric credential and private key are available locally for sign-in. Pass an `id` or `identifierHint` to check a specific credential. The function signature is: ```ts function getAvailability( params?: GetBiometricCredentialAvailabilityParams, ): Promise ``` #### Parameters `getAvailability()` accepts the following parameters (`GetBiometricCredentialAvailabilityParams`): | Name | Type | Description | | --------------- | ------ | ------------------------------------------------------------------------------------------------------- | | id? | string | The ID of the biometric credential to check. When omitted, Clerk checks the available local credential. | | identifierHint? | string | A local-only user identifier hint used to select a matching credential. | #### Returns `getAvailability()` returns the following values: | Name | Type | Description | | ----------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------ | | isAvailable | boolean | Whether a local credential and private key are available for biometric sign-in. | | unavailableReason | 'environment\_unavailable' | 'native\_api\_disabled' | 'feature\_disabled' | 'unsupported\_platform' | 'biometric\_authentication\_unavailable' | 'no\_local\_credential' | 'local\_key\_missing' | 'server\_credential\_missing' | 'server\_credential\_revoked' | null | The reason biometric sign-in is unavailable. This value is null when sign-in is available. | ### `list()` Lists active biometric credentials for the signed-in user. Returns a `Promise` that resolves to an array of [BiometricCredential](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#biometric-credential) objects. The function signature is: ```ts function list(): Promise ``` ### `enroll()` Enrolls the current app installation as a biometric credential. Enrollment requires a Clerk session with a status of `active` or `pending`. Returns a `Promise` that resolves to the enrolled [BiometricCredential](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#biometric-credential) object. The function signature is: ```ts function enroll(params?: EnrollBiometricCredentialParams): Promise ``` #### Parameters `enroll()` accepts the following parameters (`EnrollBiometricCredentialParams`): | Name | Type | Description | | ---------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------- | | name? | string | A human-readable name stored with the biometric credential. | | identifierHint? | string | A local-only user identifier hint stored with the credential for later selection. | | reason? | string | The reason displayed in the system authentication prompt. | | 'biometry\_current\_set': Requires a biometric from the currently enrolled set. Adding or removing biometric enrollment invalidates the private key. | 'biometry\_any': Requires biometric authentication and allows biometric enrollment changes. | | ### `revoke()` Revokes a biometric credential. If the credential belongs to the current app installation, Clerk also deletes its local private key. Returns a `Promise` that resolves to the revoked [BiometricCredential](https://clerk.com/docs/expo/reference/native-hooks/use-biometric-credentials.md#biometric-credential) object. The function signature is: ```ts function revoke(id: string): Promise ``` #### Parameters `revoke()` accepts the following parameter: | Name | Type | Description | | ---- | ------ | --------------------------------------------- | | id | string | The ID of the biometric credential to revoke. | ### `signIn()` Signs in with a locally enrolled biometric credential. The function signature is: ```ts function signIn(params?: SignInWithBiometricsParams): Promise ``` #### Parameters `signIn()` accepts the following parameters (`SignInWithBiometricsParams`): | Name | Type | Description | | --------------- | ------ | --------------------------------------------------------------------------------------------------- | | id? | string | The ID of the biometric credential to use. When omitted, Clerk uses the available local credential. | | identifierHint? | string | A local-only user identifier hint used to select a matching credential. | | reason? | string | The reason displayed in the system authentication prompt. | #### Returns `signIn()` returns the following values: | Name | Type | Description | | ---------------- | -------------- | ------------------------------------------------------------------------------------------------------------- | | status | SignInStatus | The status of the sign-in attempt. | | createdSessionId | string | null | The ID of the session created by a completed sign-in. Pass this value to setActive() to activate the session. | ## Types ### `BiometricCredential` | Name | Type | Description | | ------------- | --------------------- | --------------------------------------------------------- | | id | string | The ID of the biometric credential. | | object | 'trusted\_device' | The resource object name. | | platform | 'ios' | 'android' | The platform associated with the credential. | | appIdentifier | string | The native app identifier associated with the credential. | | name | string | null | The human-readable credential name. | | algorithm | 'ES256' | The credential's signature algorithm. | | status | 'active' | 'revoked' | The credential's status. | | createdAt | Date | The date when the credential was created. | | updatedAt | Date | The date when the credential was last updated. | | lastUsedAt | Date | null | The date when the credential was last used. | | revokedAt | Date | null | The date when the credential was revoked. | ## How to use the `useBiometricCredentials()` hook To learn how to enroll a biometric credential, sign in a returning user, and revoke a credential, see the [biometric sign-in guide](https://clerk.com/docs/guides/development/custom-flows/authentication/biometric-sign-in.md). --- ## Sitemap [Overview of all docs pages](https://clerk.com/docs/llms.txt)