Google Consent Mode V2 

Basic vs Advanced Mode 

There are two ways to implement Consent Mode V2:

Basic Mode (Recommended by me)

Google Tag Manager only loads after the user gives consent. No data is sent to Google before consent. This is the GDPR-safe approach because no connection to Google servers is made until the user explicitly opts in.

Advanced Mode (Recommended by Google)

Google Tag Manager loads on every page visit with all consent signals set to denied. Google still receives cookieless pings for modeled conversions, even without user consent. This may not be GDPR compliant because data is transmitted to Google servers before the user has given consent.

Why you must use window.gtag 

The cookie manager executes opt_in_code and opt_out_code inside JavaScript callback functions (onAccept and onChange). This causes two problems with a bare function gtag(){} declaration:

1. Function Scoping

A function gtag(){} declaration inside a callback is scoped to that callback. It does not become available on window, so other code blocks (like opt_out_code) cannot access it.

2. Function Hoisting (the hidden trap)

JavaScript hoists function declarations to the top of their enclosing function - even when they appear inside an else branch. This means the cookie manager's generated code looks like:

// Generated onChange callback (simplified)
cf_cookieconfig.onChange = function(cookie, changed_preferences) {
  // JavaScript hoists "function gtag(){}" from the else branch to HERE
  // creating a local variable: var gtag = undefined;

  if (!cc.allowedCategory('googletagmanager')) {
    // OPT-OUT BRANCH
    // typeof gtag === 'function' → FALSE (local gtag is undefined, NOT window.gtag)
    // The denied signal is NEVER sent!
  } else {
    // OPT-IN BRANCH
    function gtag(){dataLayer.push(arguments);}  // hoisted above!
  }
};

Copied!

The hoisted function gtag(){} creates a local variable gtag = undefined that shadows window.gtag in the entire callback - including the opt-out branch where it was never assigned. This is why typeof gtag === 'function' fails even when window.gtag exists.

The fix: Use window.gtag everywhere. The assignment window.gtag = function(){...} is not hoisted and explicitly places the function on the global object. Referencing window.gtag in opt_out_code bypasses the local scope entirely.

Service Architecture 

Consent Mode signals are Google-specific. Other marketing providers (Facebook Pixel, LinkedIn Insight, TikTok, etc.) do not use gtag consent mode - they manage their own consent through their own scripts.

In the cookie manager, opt_in_code and opt_out_code live on Services, not on Categories. This means you cannot add consent mode code to a category directly. Instead, you create dedicated services for the consent mode signals.

The recommended service structure:

The Google Consent Mode services in Marketing and Functional are lightweight - they do not load any scripts or set any cookies. They only exist to fire the window.gtag('consent', 'update', ...) calls when the user toggles that category. Other providers in the same category manage their own loading/unloading independently.

Basic Mode Setup (Recommended) 

window.dataLayer = window.dataLayer || [];
window.gtag = function(){dataLayer.push(arguments);};

window.gtag('consent', 'default', {
  'security_storage': 'denied',
  'functionality_storage': 'denied',
  'personalization_storage': 'denied',
  'analytics_storage': 'denied',
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied'
});

var script = document.createElement('script');
script.type = 'text/javascript';
script.async = true;
script.src = 'https://www.googletagmanager.com/gtm.js?id=[##GT_TRACKING_ID##]';
script.onload = function() {
  window.gtag('js', new Date());
  window.gtag('config', '[##GT_TRACKING_ID##]');

  window.gtag('consent', 'update', {
    'analytics_storage': 'granted'
  });
};
document.head.appendChild(script);

window.gtag('consent', 'update', {
  'analytics_storage': 'denied'
});

window.gtag('consent', 'update', {
  'ad_storage': 'granted',
  'ad_user_data': 'granted',
  'ad_personalization': 'granted'
});

window.gtag('consent', 'update', {
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied'
});

window.gtag('consent', 'update', {
  'functionality_storage': 'granted',
  'security_storage': 'granted',
  'personalization_storage': 'granted'
});

window.gtag('consent', 'update', {
  'functionality_storage': 'denied',
  'security_storage': 'denied',
  'personalization_storage': 'denied'
});

Advanced Mode Setup 

In Advanced Mode, the Tag Manager and consent defaults are loaded globally on every page via TypoScript, before any consent is given. The cookie manager services then fire consent update calls when the user opts in or out.

page.headerData {
  99 = TEXT
  99.value (
    <script>
      window.dataLayer = window.dataLayer || [];
      window.gtag = function(){dataLayer.push(arguments);};

      window.gtag('consent', 'default', {
        'security_storage': 'denied',
        'functionality_storage': 'denied',
        'personalization_storage': 'denied',
        'analytics_storage': 'denied',
        'ad_storage': 'denied',
        'ad_user_data': 'denied',
        'ad_personalization': 'denied'
      });
    </script>
    <script async src="https://www.googletagmanager.com/gtm.js?id=YOUR-GTM-ID"></script>
    <script>
      window.gtag('js', new Date());
      window.gtag('config', 'YOUR-GTM-ID');
    </script>
  )
}

window.gtag('consent', 'update', {
  'analytics_storage': 'granted'
});

window.gtag('consent', 'update', {
  'analytics_storage': 'denied'
});

window.gtag('consent', 'update', {
  'ad_storage': 'granted',
  'ad_user_data': 'granted',
  'ad_personalization': 'granted'
});

window.gtag('consent', 'update', {
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied'
});

window.gtag('consent', 'update', {
  'functionality_storage': 'granted',
  'personalization_storage': 'granted'
});

window.gtag('consent', 'update', {
  'functionality_storage': 'denied',
  'personalization_storage': 'denied'
});

Testing Consent Mode 

• Go to your Tag Manager Admin page to test the Consent Mode configuration.

  • Open https://tagmanager.google.com/# and select your account or tag to open the admin page.
  • Open the Tag Manager Configuration Page.

  

  • Select the "Administration" Tab and open the "Container Settings" section.

  

  • Press the "Enable Consent Mode" Button to enable the consent mode updates.

  

  • Switch back to your "Workspace" and open the "Preview / Debug" mode. And open your website in the new opened tab. (Accept all cookies in the cookie manager to see the default state of the consent mode signals)

  

  • Opt Out in the Cookie Manager in your TYPO3 Frontend to load the Tag Manager with all consent signals set to granted. (Just accept all)

  

  • Opt Out some categories or deny all in the Cookie Manager in your TYPO3 Frontend:

  

  • Try some combinations of accepted and denied categories in the Cookie Manager in your TYPO3 Frontend:

  

With this setup, you can verify that the correct consent signals are being sent to Google based on the user's choices in the cookie manager. You should see the consent updates reflected in the Tag Manager debug console as you toggle different categories on and off, confirming that the integration is working as expected. You can Customize the opt-in and opt-out code to fit your specific tag needs, such as adding additional consent signals or integrating with other marketing providers.

Hope this helps you get started with Google Consent Mode V2 in the CodingFreaks cookie manager! If you have any questions or need further assistance, feel free to ask or join our community Slack channel in the Typo3 Ecosystem.

Links 

• Google Consent Mode V2 Documentation: https://developers.google.com/tag-platform/devguides/consent
• Google Tag Manager Admin Page: https://tagmanager.google.com/
• CodingFreaks TYPO3 Slack Channel: https://typo3.slack.com/archives/C04NB2ZP30U
• Google Consent Mode V2 YouTube Tutorial: https://www.youtube.com/watch?v=MqAEbshMv84