Mailchimp for WordPress Form GTM Event Listener

Mailchimp for WordPress (MC4WP)

Overview

Mailchimp for WordPress (MC4WP) is a popular WordPress plugin for adding Mailchimp subscription forms. It exposes a comprehensive JavaScript API with events for success, error, subscribe, unsubscribe, and form start. This listener captures all five events with form ID and name.

Events fired:

• MailchimpFormSuccess, form submitted successfully
• MailchimpFormSubscribed, subscription processed
• MailchimpFormError, submission error
• MailchimpFormUnsubscribed, unsubscription processed
• MailchimpFormStarted, user begins filling form (abandonment tracking)

Variables: formID, formName

Why Use This Listener

MC4WP's multi-event system gives you granular insight into the entire subscription lifecycle, from form engagement to confirmation. The MailchimpFormStarted event is particularly valuable for calculating form abandonment rates.

Common Use Cases

• Track newsletter sign-ups as GA4 conversions
• Measure form start-to-completion rates (abandonment analysis)
• Monitor subscription errors and fix broken forms
• Fire Lead events to Meta on successful subscription
• Build audiences of subscribers for retargeting

Installation

<!-- GTM Custom HTML Tag: Mailchimp for WP Listener -->
<script>
(function() {
  function mcPush(eventName, form) {
    window.dataLayer = window.dataLayer || [];
    window.dataLayer.push({
      'event': eventName,
      'formID': form.id,
      'formName': form.name
    });
  }
  
  mc4wp.forms.on('success', function(form) { mcPush('MailchimpFormSuccess', form); });
  mc4wp.forms.on('subscribed', function(form) { mcPush('MailchimpFormSubscribed', form); });
  mc4wp.forms.on('error', function(form) { mcPush('MailchimpFormError', form); });
  mc4wp.forms.on('unsubscribed', function(form) { mcPush('MailchimpFormUnsubscribed', form); });
  mc4wp.forms.on('started', function(form) { mcPush('MailchimpFormStarted', form); });
})();
</script>

Fire on: DOM Ready.

Data Layer Output

{
  "event": "MailchimpFormSuccess",
  "formID": 1,
  "formName": "Homepage Newsletter"
}

Triggers to Create

Variables to Capture

GA4 Mapping

Debugging

Best Practices

1. Use MailchimpFormSuccess for conversion tracking, not MailchimpFormSubscribed, success is more reliable
2. Track MailchimpFormStarted to calculate form abandonment in GA4
3. Track MailchimpFormError in GA4 as a custom event to monitor form health

Related Listeners

• ConvertKit
• Klaviyo
• Omnisend