There’s no denying that Google Tag Manager (GTM) is a powerful tool for marketers, analysts and developers alike. It streamlines the process of adding, editing and managing tags on your website or app – all without needing to modify the codebase directly. However, while GTM simplifies tracking and analytics implementation, it’s easy to fall into common traps during setup that can lead to inaccurate data, broken functionality, or missed insights.
Whether you’re a digital marketing novice or an experienced strategist, avoiding these common mistakes will help you get the most out of GTM right from the start. If you’re in the early stages of implementing GTM, keep this list handy to ensure a clean, reliable setup.
Not Using a Proper Naming Convention
When creating tags, triggers and variables, it’s essential to use a clear and consistent naming structure. Avoid vague names like “Tag 1” or “Click Trigger.” As your GTM container grows, a messy structure makes it hard to track what each item does – especially when working in teams or revisiting the container months later.
Best practice: Use names that describe the tag’s function and associated platform. For example:
- “GA4 – Pageview – All Pages”
- “Meta – Conversion – Lead Form Submit”
- “Trigger – Click – Contact Button”
This simple habit can save hours of troubleshooting down the track.
Ignoring Built-in Variables
GTM provides a suite of built-in variables that cover everything from click elements to page paths and referrers. Many beginners make the mistake of not enabling or using them effectively, which often leads to redundant custom variables being created unnecessarily. Head to Variables > Configure and tick all the built-in variables relevant to your needs – this gives you immediate access to a wealth of data without reinventing the wheel.
Overloading One Container with Tags for Multiple Sites
It may seem efficient to manage multiple websites or clients in a single GTM container, but this approach can cause serious confusion (and worse, accidental data leaks across properties). Each GTM container should be tied to one website or app – this ensures cleaner data governance, easier troubleshooting, and better alignment with your platform’s unique goals.
Failing to Set Up Environments
GTM allows you to create environments like ‘Live’, ‘Staging’ and ‘Development’ – a crucial feature for testing new tags before deploying them to your live site. Skipping this step is a common mistake that often results in broken tags or data being sent prematurely to your analytics platforms. To avoid this, set up GTM environments and work within them to safely test your changes before publishing.
Not Using Preview Mode Properly
Before publishing any changes, the GTM Preview mode should be your best friend. It lets you test your setup in real-time to confirm that tags are firing correctly, triggers are working as expected, and variables are capturing the right data. It’s surprising how often users skip this step or don’t use it effectively. Doing so can result in inaccurate tracking – or even worse, tracking nothing at all.
Tip: Always check the Preview console after any updates. If something doesn’t fire or data appears incorrectly, fix it before publishing.
Forgetting to Link GTM with GA4 Properly
With the shift to Google Analytics 4 (GA4), many users assume that just placing the GA4 tag in GTM is enough. But GA4’s event-driven model requires more nuance. You need to define specific events, configure parameters correctly, and ensure your GA4 property is set up to recognise them. Misconfigured GA4 tags are among the most common culprits for lost data. Take time to map out the key events you want to track and ensure they’re implemented properly within both GTM and GA4.
Not Versioning or Documenting Changes
GTM allows you to create versions of your container every time you publish – however, many users overlook the importance of version control and clear documentation of what was changed and why. Not doing so can make it extremely difficult to roll back errors or understand the history of your setup. Always leave a descriptive version name and note, and keep an external log or change tracker if you’re managing GTM for clients or across teams.
Using Too Many Tags Without Organisation
While it’s tempting to throw in as many tags as needed (especially when running multiple campaigns) a cluttered container becomes difficult to manage. Without a clear hierarchy or folder structure, you risk duplicate or conflicting tags firing, which can skew your data or affect site performance. Take the time to categorise and label your tags. GTM now supports workspaces and folders to help you organise your container more efficiently.
Not Testing Across Devices and Browsers
Even if everything looks good in GTM Preview and works on desktop, that doesn’t mean it’ll work everywhere. Tags, triggers or elements can behave differently depending on the device, screen size, or browser type. Be sure to test your setup across multiple environments – including mobile and tablet – to ensure consistent functionality.
Giving Too Many People Full Access
Collaboration is essential in digital projects, but not everyone should have full access to publish or edit GTM containers. Mistakes can (and do) happen, especially if multiple people are working within the same workspace without coordination. Use GTM’s built-in user roles and permissions to control access. Grant ‘View’ or ‘Approve’ access where possible, and restrict ‘Publish’ rights to experienced team members.
Ready to get started?
Google Tag Manager is a flexible, user-friendly tool – but it’s only as effective as the care taken during setup. Avoiding these common mistakes helps ensure your tags fire correctly, your analytics stay clean, and your campaigns perform optimally. A well-configured GTM setup can unlock powerful insights and allow your business to track what truly matters… so set the foundation right, and let your data do the talking.
