How to Implement Google Consent Mode V2 with Digital Markets Act Compliance

Common Implementation Errors

You may encounter several common errors during the implementation of Google Consent Mode V2. One such error is “A tag read consent state before default was set”. This error occurs when the default consent state has not been defined or properly configured during the setup of the CMP Tag in Google Tag Manager (GTM). It can also happen if you’ve used the Custom Script method to implement GCM and the custom script is missing from your website.

Another potential issue is the “Consent not updating” error. This error occurs when the consent preferences of users are not properly updated or recorded. To resolve this, ensure that you have enabled “Support GCM” from the CMP dashboard and submitted and published the changes. Additionally, verify that the CMP tag is fired first, before any other tags on the website, and update the CMP tag script to the latest version (Consent Mode v2).

The “Tag firing before consent initialization” error occurs when other tags are read or fired before the default consent is set. To fix this, ensure that the trigger “Consent Initialization – All pages” is set only for the CMP Tag, allowing it to fire first before any other tags. Verify that all directly loaded tags are fired only after GTM is completely loaded by using the Tag Assistant debug console.

Debugging with Google Tag Assistant

Google Tag Assistant is a powerful tool that can help you verify and troubleshoot your consent mode implementation on your website. With Tag Assistant, you can check:

• Whether your website sets the correct default consent state before any tags fire.
• Whether your website updates consent states correctly after visitors grant or deny consent.
• Which tags check for which consent types.
• Whether the required consent types were granted when each tag triggered, and whether the tag passed the checks for any additional required consent.

To verify your consent setup using Tag Assistant, follow these steps:

1. Open Google Tag Assistant and enter your website’s URL.
2. On your website, open the cookie banner and accept all.
3. In Tag Assistant, verify if the page set the default consent correctly by checking the “API Call” section or the “Consent” tab in the “Output” of your tag section.
4. Verify if the page updated the consent based on your consent banner interaction by checking the most recent “Consent” event in the “API Call” section or the “Consent” tab.
5. Check which tags fired or were blocked by the consent state by selecting the “Tags” tab and clicking on individual tags.

Best Practices for Smooth Implementation

To ensure a smooth implementation of Google Consent Mode V2, follow these best practices:

• Set the default consent state for all consent mode parameters (ad_storage, analytics_storage, ad_user_data, and ad_personalization) to ‘denied’ before any tags fire. This ensures no data is collected without explicit consent.
• Move all code that calls gtag(‘consent’, ‘default’, …) commands higher in the page, above any tag snippets or other code that might be using consent.
• Use the gtag.js update command to update the consent state after a visitor interacts with your consent banner. Ensure you have an update mechanism for every parameter you set a consent default for.
• If using a Consent Management Platform (CMP) tag template in GTM, check the CMP documentation for setting default consent and updating consent states.
• Verify consent mode works for different user regions by setting your visitor location and checking if consent mode adapts accordingly.

By following these guidelines and leveraging tools like Google Tag Assistant, you can effectively troubleshoot and resolve common issues that may arise during the implementation of Google Consent Mode V2, ensuring compliance with data privacy regulations and respecting user consent preferences.