Google Pay Hosted Checkout


Google Pay Hosted Checkout is our simple integration that enables online Google Pay processing through the Cardknox gateway. This document details the steps necessary to integrate Google Pay Hosted Checkout with your site.


  • Server-Side Integration

    • Server Endpoint Creation

    • API Integration

  • Client-Side Integration

    • Adding Reference to iFields

    • Adding iFrame and JavaScript objects for the Google Pay button

    • Enabling Google Pay

Implementing Google Pay Hosted Checkout

Server-Side Integration

Server Endpoint Creation

A server endpoint is needed in order to accept the Google Payload from Hosted Checkout.

Step 1: Create an endpoint and method for API Integration on your server side that takes the Google Payload and makes a call to Cardknox.

API Integration

Below are the steps to integrate Google Pay with the Cardknox API:

Once the consumer confirms the payment, Google Pay API generates a token in the form of a JSON string.

Integration Steps:

  1. Encode that token with Base64 encoding.

  2. Set xCardNum field to the encoded token above.

  3. Set xDigitalWalletType to GooglePay.

  4. Set the remaining required fields:

    1. xAmount to transactionInfo.totalPrice - this is the consumer-approved amount from the Google Pay payment sheet.

    2. xCommand - Set to one of the values that start with cc: like cc:sale, cc:auth, etc.

    3. xBillFirstName

    4. xBillLastName

    5. xBillStreet if available

    6. xBillCity if available

    7. xBillState if available

    8. xBillZip

For more details, please contact your Cardknox Representative.

Client-Side Integration

Adding Reference to iFields

Find the latest version of iFields here.

Step 1: Add the iFields .js file after the <head> tag on your payment page:

<script src=**ifields-version-number**/ifields.min.js></script>

Adding iFrame and JavaScript Objects for Google Pay button

Step 1: Add the following iFrame JS snippet inside the <body> where the Google Pay button is desired.

  • Make sure you have an attribute data-ifields-id="igp" as part of <iframe> tag

  • Make sure you have an attribute data-ifields-oninit="gpRequest.initGP" as part of <iframe> tag where “gpRequest.initGP“ is a function name that initializes a Google Pay Object

<iframe id="igp" class="gp hidden" 
data-ifields-id="igp" data-ifields-oninit="gpRequest.initGP" 
allowpaymentrequest sandbox="allow-popups allow-modals allow-scripts allow-same-origin
allow-forms allow-popups-to-escape-sandbox allow-top-navigation"> 

Step 2: Create JavaScript object that holds all of the properties/methods required to process Google Pay.

const gpRequest = {
merchantInfo: {
merchantName: "Example Merchant"
buttonOptions: {                               
buttonSizeMode: GPButtonSizeMode.fill
billingParams: {
//phoneNumberRequired: true,
emailRequired: true,
billingAddressRequired: true,                               
billingAddressFormat: GPBillingAddressFormat.full                                        

Full a full sample code, refer to the iFields document.

Step 3: Implement desired callbacks.

For the list of available callbacks, please refer to Google Pay Object.

  • The two main functions below need to be implemented (the rest are optional):

    • onGetTransactionInfo: calculates the total amount based on the charge amount, fees, taxes, shipping costs, etc.

    • onProcessPayment - a callback that will be called after the consumer pays and Google returns a token with all other requested consumer information like billing address, shipping address, etc. This is where you need to make an ajax call to your server with the Google Payload. The sample for making an ajax call please see below.

Sample Code for making Ajax Call:

initGP: function authorizeGPay(googlePayload) {
    return new Promise(function (resolve, reject) {
        var xhr = new XMLHttpRequest();"POST",;
        xhr.onload = function () {
            if (this.status >= 200 && this.status < 300) {
            } else {
                    status: this.status,
                    statusText: xhr.statusText
        xhr.onerror = function () {
                status: this.status,
                statusText: xhr.statusText
        xhr.setRequestHeader("Content-Type", "application/json");

For full sample code, please refer to Google Pay Sample Code.

Step 4: Create JavaScript function that will initialize iFields.

function initGP() {

    return {
        merchantInfo: gpRequest.merchantInfo,
        buttonOptions: gpRequest.buttonOptions,
        onGetTransactionInfo: "gpRequest.onGetTransactionInfo",
        environment: gpRequest.environment,
        billingParameters: gpRequest.billingParams,
        shippingParameters: {
            emailRequired: gpRequest.shippingParams.emailRequired,
            onGetShippingCosts: "gpRequest.shippingParams.onGetShippingCosts",
            onGetShippingOptions: "gpRequest.shippingParams.onGetShippingOptions"

        onBeforeProcessPayment: "gpRequest.onBeforeProcessPayment",
        onProcessPayment: "gpRequest.onProcessPayment",
        onPaymentCanceled: "gpRequest.onPaymentCanceled",
        onGPButtonLoaded: "gpButtonLoaded"

Make sure that the iFrame attributedata-ifields-oninit has the name of this function.

The initGP() function above returns Google Pay Object.

Enable Google Pay

window.ckGooglePay object - controls initialization of Google Pay button.


Call Required




Initializes and enables Google Pay Button. Takes EnableGooglePayParams object



Updates amount on Google Sheet.

You can provide either All, One or None of the parameters for enableGooglePay call.

  • amountField specified - in this case, the Google Pay total amount will be automatically updated whenever the amount has changed.

  • amountField is not specified - in this case, it’s up to you to provide the correct amount for Google Pay. One of the ways to do it is to call window.ckGooglePay.updateAmount manually.

  • iframeField specified - this value will be used to communicate, with Google Pay button. This option is especially helpful for Angular clients using shadow DOM.

  • iframeField is not specified - its value will be calculated based on data-ifields-id attribute. In this case, it must be set to “igp“: data-ifields-id="igp".

EnableGooglePayParams Object








Field containing amount. Could be either the name of the field (String) or the field itself (Object)




Field containing iFrame with Google Pay button. Could be either the name of the field (String) or the field itself (Object)

Enable Google Pay example

ckGooglePay.enableGooglePay({amountField: 'amount'});


Check out the Google Pay FAQ page here.

For additional questions, contact

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