> 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/face-liveness.md).

# Face Liveness

Install and launch Face Liveness for React Native. Learn prerequisites, CerttaLivenessConfiguration options, hook events, success and failure results, and error handling.

{% hint style="warning" %}
This guide covers **@caf.io/react-native-sdk 5.4.0** and above (Certta DevX). For the previous sequential `useCafSdk` flow, see the [legacy documentation](https://docs.caf.io/caf-sdk/react-native/getting-started-with-the-sdk).
{% endhint %}

## Prerequisites

Before proceeding, ensure the Certta SDK is properly installed. If you haven't done this yet, please refer to our Installation Guide.

{% content-ref url="/pages/tC8MaVHQnCi3YdHr6s0p" %}
[Installation Guide](/caf-sdk/react-native/installation-guide.md)
{% endcontent-ref %}

Enable `faceLiveness` (and `faceLivenessUI` if you want the built-in UI) in `caf-modules-config.json`. You must include at least one liveness provider.

## Starting Liveness

Use the `useCafFaceLiveness` hook and call `open()` with a `CerttaLivenessConfiguration` object. The hook subscribes to native events automatically — read results from the `event` state.

{% hint style="info" %}
Set `useFaceLivenessUi` to `true` to use the built-in Certta UI. When `false`, the SDK runs the headless Face Liveness module.
{% endhint %}

```typescript
import { useEffect } from 'react';
import { useCafFaceLiveness } from '@caf.io/react-native-sdk';

function LivenessScreen() {
  const { open, event } = useCafFaceLiveness();

  useEffect(() => {
    if (event.success) {
      // Handle success — event.success.response is a JWT
    } else if (event.failed) {
      // Handle business failure — see Handling Failures
    } else if (event.error) {
      // Handle technical error
    }
  }, [event]);

  const startLiveness = async () => {
    try {
      await open({
        maxRetryAttempts: 3,
        faceAuthEnabled: false,
        showLoading: true,
        useFaceLivenessUi: true,
      });
    } catch {
      // Handle BRIDGE_EXCEPTION
    }
  };

  // ...
}
```

`open()` rejects with `CerttaPlatformException` and code `BRIDGE_EXCEPTION` when the native mapper rejects the configuration.

### `CerttaLivenessConfiguration` parameters

| Parameter           | Default | Description                                                        |
| ------------------- | ------- | ------------------------------------------------------------------ |
| `maxRetryAttempts`  | `3`     | Maximum retries after a failed capture attempt.                    |
| `faceAuthEnabled`   | `false` | When **enabled**, the SDK performs **face authentication**.        |
| `showLoading`       | `true`  | Shows loading indicators during processing when **true**.          |
| `useFaceLivenessUi` | `false` | If **enabled**, the SDK uses the built-in Certta Face Liveness UI. |
| `payFaceDebugMode`  | `false` | Enables debug mode for the PayFace provider. **iOS only**.         |

## Understanding Liveness events and results

{% hint style="warning" %}
Ensure the JWT response is evaluated on the backend. This process must include validating the token's signature and verifying the `isAlive` and `isMatch` fields. Do not perform these validations on the client side.
{% endhint %}

The hook `event` object has at most one populated field:

### `success` (`CerttaSuccess`)

The capture and liveness pipeline succeeded. **`response`** is a JWT with the result data from the Liveness execution.

### `failed` (`CerttaLivenessFailure`)

Liveness ran, but the outcome is a business failure.

| Field         | Description                                                                                            |
| ------------- | ------------------------------------------------------------------------------------------------------ |
| `type`        | `CerttaLivenessFailureType.ImageCaptureFailure` or `CerttaLivenessFailureType.FaceRecognitionFailure`. |
| `cause`       | Identifier for diagnostics or UX messaging (for example `TOO_DARK`). Uppercased by the RN plugin.      |
| `description` | Optional human-readable description from the native SDK.                                               |
| `response`    | Signed payload. Present for `FaceRecognitionFailure` when capture succeeded but recognition failed.    |

{% hint style="info" %}
To understand and handle the `cause` of the failure, see [Handling Failures](/caf-sdk/react-native/face-liveness/handling-failures.md).
{% endhint %}

### `error` (`CerttaError`)

Triggered when a technical blocker prevents the SDK from starting or finishing the process.

| Field   | Description                                       |
| ------- | ------------------------------------------------- |
| `type`  | Error identifier mapped from the native SDK.      |
| `cause` | Additional context for the failure, when present. |

| Event                 | Typical cause                                                                                                                       |
| --------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
| `InitializationError` | **`configure`** not called, empty token or user ID, or invalid **`maxRetryAttempts`**.                                              |
| `PermissionError`     | Camera (or related) permission denied.                                                                                              |
| `NetworkError`        | Connectivity or server-side issues surfaced as network class errors.                                                                |
| `SecurityError`       | Security checks failed.                                                                                                             |
| `UnknownError`        | Other failures not mapped to a specific case.                                                                                       |
| `Cancelled`           | Occurs when the user abandons the flow before completion, such as by pressing the back button or sending the app to the background. |


---

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