GTM Setup Errors That Can Ruin Your Tracking in 2025 (Part 2)

Google Tag Manager (GTM) plays a crucial role to track your user journey and build strong reporting without requiring website developers' efforts. In Part 1 of Google Tag Manager mistakes, we discussed  Part  a robust tool designed to manage tags and tracking codes across both websites and mobile applications. It serves as a centralized tag management system that enables the deployment of multiple tracking codes and facilitates data sharing with platforms like Google Analytics, Google Ads, SA360, Facebook/Meta, Snapchat, and many others.

However, during GTM implementation, some key features may be overlooked or underutilised, which can lead to tracking issues or inefficient setups. Many businesses encounter common mistakes during the GTM setup process that compromise the accuracy and effectiveness of their tagging strategy.

We’ll walk you through some of the most common Google Tag Manager (GTM) mistakes and provide practical, step-by-step tips to help you prevent them. Let’s explore each one in detail.

1. Hardcoded Snippets on the page

Leaving hardcoded tracking snippets on your site and also setting up the same tracking tags via GTM can result in double-counting metrics and inaccurate data.

Hardcoded snippets on the page

Best Practice: Always remove any hardcoded tracking snippets from your site when migrating those tags into GTM. This avoids duplication, ensures clean and accurate tracking, and consolidates all tag management in a single, manageable platform.

Centralizing tracking through GTM not only reduces clutter but also makes troubleshooting, updates, and tag governance significantly easier.

2. Failing to Publish the GTM Container

Failing to publish the GTM container can result in displaying an outdated version of the container, causing tracking issues and data discrepancies.

Best Practice: Always publish the GTM container after making changes and verify that the latest version is live. This ensures your updates are properly deployed and your tracking remains accurate and up to date.

Publishing regularly maintains data integrity and avoids confusion caused by outdated setups still being used in the live environment.

Publish Latest version in GTM

3.  Using Inaccurate Attributes to Configure Triggers

Using non-specific or frequently changing classes, IDs, or elements can lead to configuration breakages.

Inaccurate attributes

Best Practice: Always use stable and descriptive attributes (like unique IDs, persistent class names, or data attributes) when configuring triggers. This ensures your setup remains reliable and continues to function correctly even after website updates or design changes.

Accurate attributes

4. Not Applying Conditional validation when writing HTML tags.

Failing to implement conditional validation can break your HTML code and trigger errors in the browser console, potentially affecting site functionality and user experience.

Conditional validation is missing

Best Practice: Always apply conditional validation when inserting tags or running scripts that depend on specific elements or values. This ensures your code runs only when the required conditions are met, preserving HTML integrity and avoiding unnecessary console errors.

Implementing validation improves the reliability of your tags and reduces the chances of front-end disruptions due to unexpected conditions.

Applied conditional validation

5. GTM datalayer  Snippet Pushed After Firing the Tag

Pushing the GTM datalayer snippet after firing the tag can cause implementation issues, resulting in no data being captured by the event.

Example:

In one scenario, the developer implemented a dataLayer push from the backend. However, the dataLayer was pushed before the GTM script had loaded on the website. As a result, GTM was not available at the time of the push, and the associated event did not fire as expected.

Best Practice: Always ensure the dataLayer.push() occurs before the tag is fired. This guarantees that the tag has access to all the necessary event information at the time it executes.

Proper sequencing of dataLayer.push() and tag firing is critical for reliable tracking and accurate data collection.

6. Not Checking Real-Time Reports

Neglecting to check real-time reports can lead to missed errors and data discrepancies in your tracking setup.

Best Practice: After making any changes in GTM, always validate tag firing in the GTM preview/debug mode and verify data flow in GA4’s real-time reports. This ensures your setup is functioning as expected and helps catch issues early, before they impact business reporting or campaign performance.

Real-Time reports

7. GTM Container Not Present on the Site

Making all the tag configurations but not deploying the GTM container snippet on the website. Nothing will fire, and the whole setup becomes inactive.

Best Practice: Always verify that the GTM container snippet is correctly installed and loaded in both the <head> and <body> sections of your website before starting any tag implementation.

This ensures that GTM can execute your configured tags and triggers properly, avoiding wasted time and data loss.

The GTM container snippet is present on the website

Conclusion:

By proactively addressing these common issues and applying the recommended best practices, you can significantly enhance the efficiency and reliability of your Google Tag Manager setup. This leads to more accurate and consistent data tracking across your website, reduces the risk of errors or data loss, and simplifies long-term tag management.