> 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/sdk-response.md).

# SDK Response

Reference for the SDK response JWT. Learn payload fields, signature validation, and result checks.

### JWT & Signing

A JSON Web Token (JWT) is a compact, secure standard for transmitting information between a client and a server as a JSON object.

### Response parameters

The SDK returns the verification result as a JWT. To guarantee data integrity, Certta signs the JWT on the backend using a secure private key. Your backend must validate this signature before trusting the payload.

To learn more about security and secret keys, see the Authentication page:

{% content-ref url="/pages/9JinhiBRarpeMNxbUECl" %}
[Authentication](/caf-sdk/authentication.md)
{% endcontent-ref %}

### JWT payload example

A JWT has three parts: header, payload, and signature. The claims below are part of the payload.

{% tabs %}
{% tab title="JWT" %}
{% code title="" %}

```json
{
  "header": {
    "alg": "HS256",
    "typ": "JWT"
  },
  "payload": {
    "sessionId": "01KVGG0CR3928MQERDX8NGA8AEQ",
    "personId": "user-id",
    "isAlive": false,
    "isMatch": false,
    "imageUrl": "https://mobile-prod-liveness-attempts.s3.us-east-1.amazonaws.com/...",
    "createdAt": "2026-06-19T17:49:15.432Z",
    "iat": 1781895533
  },
  "signature": "LNFjtTO27Z5GLR8NhhziX3nE8kftoemUOfkICkk5w8Q"
}
```

{% endcode %}
{% endtab %}

{% tab title="Raw String" %}
{% code title="response" %}

```
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.LNFjtTO27Z5GLR8NhhziX3nE8kftoemUOfkICkk5w8Q
```

{% endcode %}
{% endtab %}
{% endtabs %}

| Field     | Description                                                                   |
| --------- | ----------------------------------------------------------------------------- |
| sessionId | Request identifier.                                                           |
| personId  | User identifier provided for the SDK.                                         |
| isAlive   | Indicates whether the SDK verified a live person successfully.                |
| isMatch   | Indicates whether face match succeeded. Present when face match is enabled.   |
| imageUrl  | Temporary image URL generated by the API.                                     |
| createdAt | Time when the token was created.                                              |
| iat       | Time when the token was issued.                                               |
| message   | Result message returned by the service. May be present depending on the flow. |

{% hint style="warning" %}
The validation flow depends on the `isAlive` and `isMatch` parameters when using face match. Both values must be `true` to proceed. If either value is `false`, the user is invalid and the process must be terminated.
{% endhint %}


---

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