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# applicationData

A Base64-encoded string for application-specific data.

```
DOMString applicationData;
```

## Discussion

Use this property to contain additional data as may be appropriate for your website. For example, the application data may be a shopping cart identifier or an order number that your back end needs to identify this transaction.

You’re responsible for sending the full application data to your server, if needed.

> Important:
> If you use <doc://com.apple.documentation/documentation/ApplePayWebMerchantRegistrationAPI/RegisterMerchantRequest> in the <doc://com.apple.documentation/documentation/ApplePayWebMerchantRegistrationAPI> to register merchants, you must include the merchant domain in ``doc://com.apple.applepayontheweb/documentation/ApplePayontheWeb/ApplePayRequest/applicationData``. The payment service provider can use the domain in ``doc://com.apple.applepayontheweb/documentation/ApplePayontheWeb/ApplePayRequest/applicationData`` to ensure they know which merchant the payment token is for. The payment service provider uses the value in ``doc://com.apple.applepayontheweb/documentation/ApplePayontheWeb/ApplePayRequest/applicationData`` in a step necessary to validate the payment data. For more information, see <doc://com.apple.documentation/documentation/PassKit/payment-token-format-reference>.

The [`applicationData`](/documentation/ApplePayontheWeb/ApplePayPaymentRequest/applicationData) string must be Base64-encoded; otherwise, the system ignores it.

---

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