> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crossmint.com/llms.txt
> Use this file to discover all available pages before exploring further.

# BiometricRequestHandler

<Note>
  **This page has been updated for Wallets SDK V1.** If you are using the previous version,
  see the [previous version docs](/wallets/v0/overview) or the [V1 migration guide](/wallets/guides/migrate-to-v1).
</Note>

> **BiometricRequestHandler** = (`action`) => `Promise`\<`void`>

Defined in: [packages/wallets/src/utils/device-signers/IframeDeviceSignerKeyStorage.ts:32](https://github.com/Crossmint/crossmint-sdk/blob/main/packages/wallets/src/utils/device-signers/IframeDeviceSignerKeyStorage.ts#L32)

Callback invoked before a WebAuthn ceremony to obtain user activation.
Implementations should show a UI prompt and resolve when the user interacts (e.g. clicks a button).

## Parameters

| Parameter | Type                             | Description                                                                                                       |
| --------- | -------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
| `action`  | `"createCredential"` \| `"sign"` | The biometric action being requested: `"createCredential"` for wallet creation, `"sign"` for transaction signing. |

## Returns

`Promise`\<`void`>