Add Custom Event When Consent Is Updated

[psx-dw]

Summary

When using DynamicWeb’s Cookie Manager, the function
gtag('consent', 'update', ...) is triggered whenever cookies are allowed.

However, this command does not automatically push an event to the GTM Data Layer, meaning Google Tag Manager (GTM) has no native trigger to detect when consent has been updated.

Problem

When implementing non-Google tags (e.g. third-party pixels), it’s important to have a way to trigger them immediately after consent is granted.
Since the gtag('consent', ...) command only updates Google’s internal consent state — and does not act as a general GTM event — these third-party tags currently have no way to listen for consent updates.

Proposed Solution

Add a custom Data Layer event that fires immediately after consent is updated.
This would enable GTM to trigger non-Google tags (such as marketing or tracking pixels) as soon as consent is given.

Example Implementation

// 1. Update the Google Consent Mode state
gtag("consent", "update", {
  ad_storage: "granted",
  ad_user_data: "granted",
  ad_personalization: "granted",
  analytics_storage: "granted"
});

// 2. Immediately push a custom event to the GTM Data Layer
dataLayer.push({
  event: "consent_updated" // <-- GTM can listen for this custom event
});

Benefits

• Allows non-Google tags to respect user consent while still loading immediately after it’s granted.
• Keeps consent management fully aligned with GTM best practices.
• Provides a simple, transparent mechanism for developers to integrate with existing GTM setups.

[nicped]

What if we wait to run the gtm script until after the consent update has been set?

In that way the updated consent is already set before it is send to gtm

@if (!string.IsNullOrWhiteSpace(googleTagManagerID))
{
	// Default deny until user consents
	<script>
		gtag('consent', 'default', {
			'ad_storage': 'denied',
			'ad_user_data': 'denied',
			'ad_personalization': 'denied',
			'analytics_storage': 'denied'
		});
	</script>
	
	@if (AllowTracking())
	{
		// If the user has consented, update before GTM loads
		<script>
		const adConsent = '@(CookieManager.IsCookieOptInGranted("Marketing") ? "granted" : "denied")';
		const analyticsConsent ='@(CookieManager.IsCookieOptInGranted("Statistical") ? "granted" : "denied")';

		gtag('consent', 'update', {
			'ad_storage': adConsent,
			'ad_user_data': adConsent,
			'ad_personalization': adConsent,
			'analytics_storage': analyticsConsent
		});
		</script>
	}
	<script>
		(function (w, d, s, l, i) {
			w[l] = w[l] || []; w[l].push({
				'gtm.start':
					new Date().getTime(), event: 'gtm.js'
			}); var f = d.getElementsByTagName(s)[0],
				j = d.createElement(s), dl = l != 'dataLayer' ? '&l=' + l : ''; j.defer = true; j.src =
					'https://www.googletagmanager.com/gtm.js?id=' + i + dl; f.parentNode.insertBefore(j, f);
		})(window, document, 'script', 'dataLayer', '@(googleTagManagerID)');
	</script>
	
}