Enhanced Conversions: Powerful Data Matching with GTM and Custom JavaScript

Implementing Enhanced Conversions provides a valuable opportunity for marketers to securely and effectively link offline data, such as email addresses and phone numbers, to online conversions. Using Google Tag Manager (GTM) and Custom JavaScript (CJS), you can automatically retrieve, format and send this data to Google Ads.

Notice: the collection and processing of personal data requires full compliance with the AVG/GDPR. Always ensure explicit consent through a compliant consent management platform (CMP). The following information is technical in nature and not legal advice.

Data collection and hashing: the basics

Before data is sent, personal data must be hashed. GTM performs this automatically, provided the fields are set up correctly. Make sure your input data, such as email and phone number, is clean, correct and properly formatted.

For Enhanced Conversions, you need at least one of the following:

• Email address
• Phone number
• Name and address

In this article, we focus on email and phone number retrieval via Custom JavaScript.

1. Custom JavaScript variable for email (lowercase).

In GTM, go to Variables > New > Custom JavaScript and give the variable a logical name, such as cjs_GetCustomerEmailEnhancedConversions. Then paste this code:

JavaScript

function () {
  var emailField = document.getElementById('email_field');

  if (emailField && emailField.value) {
    return emailField.value.toLowerCase().trim();
  }

  return undefined;
}
  

Important:

• Adjust the selector Based on your site (e.g. querySelector(‘input[name= email=””]’)).
• Verify that the option “Collect lowercased emails” is checked in the Enhanced Conversions variable or in the Google Ads tag.

2. Custom JavaScript variable for phone number (with country code).

In GTM, go to Variables > New > Custom JavaScript and give the variable a name such as cjs_GetCustomerPhoneEnhancedConversions. Paste this code:

JavaScript

function () {
  var phoneField = document.getElementById('phone_field');

  if (phoneField && phoneField.value) {
    let phoneNumber = phoneField.value.trim();
    phoneNumber = phoneNumber.replace(/[^0-9+]/g, '');

    if (phoneNumber.startsWith('+')) {
      return phoneNumber;
    }

    if (phoneNumber.startsWith('00')) {
      return '+' + phoneNumber.substring(2);
    }

    const defaultCountryCode = '+31';

    if (phoneNumber.startsWith('0') && phoneNumber.length > 1) {
      return defaultCountryCode + phoneNumber.substring(1);
    }

    return defaultCountryCode + phoneNumber;
  }

  return undefined;
}

Notice:

• Customize the selector to fit your HTML structure.
• Choose the correct defaultCountryCode (e.g. +32 for Belgium).