> ## 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

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

Defined in: [packages/wallets/src/utils/device-signers/IframeDeviceSignerKeyStorage.ts:34](https://github.com/Crossmint/crossmint-sdk/blob/main/packages/wallets/src/utils/device-signers/IframeDeviceSignerKeyStorage.ts#L34)

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`>