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# onvalidatemerchant

An event handler the system calls when it displays the payment sheet.

```
attribute EventHandler onvalidatemerchant;
```

## Discussion

Use this attribute to request and return a merchant session. You must set this attribute to the following function:

```javascript
session.onvalidatemerchant = function(event) {}
```

where `event` is an [`ApplePayValidateMerchantEvent`](/documentation/ApplePayontheWeb/ApplePayValidateMerchantEvent) object.

The process to complete the merchant validation is as follows:

1. Your [`onvalidatemerchant`](/documentation/ApplePayontheWeb/ApplePaySession/onvalidatemerchant) function calls your server, and passes it the static hostname `apple-pay-gateway.apple.com` as the validation URL. In the China region, use `cn-apple-pay-gateway.apple.com`.
2. Your server uses the validation URL to request a session from the Apple Pay server, as described in <doc://com.apple.documentation/documentation/ApplePayontheWeb/requesting-an-apple-pay-payment-session>.
3. In response, your server receives an opaque merchant session object, `MerchantSession`.
4. You pass the merchant session object to the completion method, [`completeMerchantValidation`](/documentation/ApplePayontheWeb/ApplePaySession/completeMerchantValidation).

The system enables the payment sheet.

> Note:
> Previous merchant validation instructions stated that your ``doc://com.apple.applepayontheweb/documentation/ApplePayontheWeb/ApplePaySession/onvalidatemerchant`` function must call your server and pass it the URL from the event’s ``doc://com.apple.applepayontheweb/documentation/ApplePayontheWeb/ApplePayValidateMerchantEvent/validationURL`` attribute. Apple Pay continues to support this flow for existing implementations.

## See Also

[Providing Merchant Validation](/documentation/ApplePayontheWeb/providing-merchant-validation)

Validate your merchant identity and receive a session object for each payment request.


---

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