> For the complete documentation index, see [llms.txt](https://docs.caf.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.caf.io/caf-sdk/react-native/standalone-modules/face-liveness/start-sdk.md).

# Start Liveness Verification

## Calling `startFaceLiveness`

To start the liveness verification, use the `startFaceLiveness` function with the mobileToken and user's document ID.

| Parameter     | Type   | Description                                                                                                                                                                                                                   | Required |
| ------------- | ------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :------: |
| `mobileToken` | string | Usage token associated with your CAF account.                                                                                                                                                                                 |     ✅    |
| `personId`    | string | Identifier of the user who will perform the face liveness verification. It's recommended to use the user's identification document in this field, such as their CPF (Brazilian document ID), but it could be any other value. |     ✅    |

### Example

```ts
<Button 
  title="Start" 
  onPress={() => startFaceLiveness(mobileToken, personId)} 
/>
```


---

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