Optimizing Scroll Tracking in Google Tag Manager: Choosing the Right Trigger Event

If you're delving into the world of Google Tag Manager (GTM), you'll quickly encounter a trio of triggers that might puzzle you: Container Load (gtm.js), DOM Ready (gtm.dom), and Window Load (gtm.load). Understanding the nuances between these triggers is crucial for ensuring your tags fire at the appropriate time, providing accurate data while optimizing website performance.

The Starting Block: Container Load (gtm.js)

When GTM's JavaScript library is fully loaded on a user's browser, the Container Load trigger springs into action. This is your first signal that GTM is in place and ready for action. However, it's essential to recognize that this trigger isn't an all-clear for all types of tags. Since the rest of the webpage might still be under construction, tags that rely on specific elements of the page should wait for a more robust cue.

The Middle Ground: DOM Ready (gtm.dom)

Once the structure of your webpage is set (meaning the HTML is fully parsed), the DOM Ready trigger is activated. This is the sweet spot for tags that need to interact with the page's elements, like tweaking the layout or capturing form inputs. It's important to note that while the DOM is ready for manipulation, some resources may still be loading, such as images or CSS files.

The Final Frontier: Window Load (gtm.load)

Patience is a virtue, and the Window Load trigger embodies this. It waits for the entire page, along with all its resources, to finish loading. This is the trigger of choice for tags that need the full scope of the webpage, such as those measuring the page's dimensions, performing complex calculations, or taking stock of all the loaded elements.

Choosing the Right Trigger

Selecting the appropriate trigger is a balancing act. On one hand, you want to capture data as early as possible, but on the other hand, you don't want to compromise on accuracy or page performance. Here's a quick guide:

• Early Bird Data Collection: Use Container Load for tags that need to fire regardless of page readiness.
• Interactivity and Form Tags: Opt for DOM Ready to ensure the elements are in place.
• Accuracy and Completeness: Reserve Window Load for when you need the entire page at your disposal.

Each trigger serves a unique purpose, and the right choice depends on the tag's function and your data requirements. By mastering the timing of your triggers, you'll unlock GTM's full potential, paving the way for insightful analytics and a seamless user experience.

Which one should we use for "scroll tracking" in the scroll trigger setting?

For "scroll tracking" in Google Tag Manager, the recommended trigger is typically the DOM Ready (gtm.dom) event. This is because scroll tracking involves measuring how far down a page a user has scrolled, and the DOM Ready event signifies that the HTML of the page has been fully loaded and parsed.

Using DOM Ready as the trigger for scroll tracking ensures that:

1. The structure of the page is in place and can be accurately measured.
2. The tracking begins as soon as the user can actually start scrolling, even if some resources like images and stylesheets haven't fully loaded yet.

The Window Load (gtm.load) event occurs later, when all resources are fully loaded. While it ensures that everything on the page has loaded, it can delay the start of scroll tracking and might miss early scroll interactions, especially on pages that take a longer time to load all resources.

Therefore, for scroll tracking, it's generally better to use the DOM Ready event, because it allows you to start tracking as soon as the user is able to interact with the page's content.