Using Google Tag Manager (GTM) to manage site speed and performance is an effective way to ensure that your website is running efficiently while still tracking the necessary data. While GTM itself doesn’t directly optimize website performance, it can be configured in ways that help reduce loading times, prevent performance issues, and streamline the implementation of tracking tags without negatively impacting site speed. Here’s how you can use Google Tag Manager to manage site speed and performance:

1. Prioritize Tag Firing Order

One of the most critical aspects of managing site performance with GTM is controlling the order in which tags are fired. Some tags, especially third-party tags, can slow down the loading of your website if not implemented properly.

• Set Firing Priority for Tags:
  • In GTM, tags are executed in the order they are triggered, which can affect page load speed. To manage this, prioritize important tags that don’t need to block page rendering (e.g., tracking, analytics) and set up less critical tags (such as ads or social tracking) to fire later.
  • Use Tag Sequencing to make sure critical tags fire first, followed by non-essential ones after the page is loaded.
  • GTM has a feature called Tag Firing Priority that allows you to adjust the sequence in which tags are executed. For example, you might want your analytics and marketing tags to fire first, and other performance-heavy tags like advertising or third-party widgets to fire later.

2. Use Asynchronous Tag Loading

Many tracking tags (such as analytics, remarketing, and other third-party scripts) can block the page from fully loading if they are not executed asynchronously. Fortunately, GTM automatically loads most of the tags asynchronously. However, some tags, especially older ones, might still be synchronous.

• Asynchronous Loading:
  • Ensure that the tags you set up in GTM are asynchronous. For most tags like Google Analytics, GTM handles this automatically. But for others, such as custom HTML tags, you can manually adjust them to load asynchronously by using the async attribute in the tag’s code.
• Defer Non-Essential Tags:
  • Tags that are not required for the immediate user experience can be deferred. For example, social media pixels, retargeting ads, or chat widgets can be loaded after the page content has loaded. GTM allows you to add triggers that delay these tags from firing until the page load is complete or after a specified time interval.

3. Lazy Load Tags

Lazy loading refers to loading non-essential resources only when they are needed, such as when a user interacts with specific elements on a page (e.g., scrolling or clicking). By deferring the loading of tags until user interaction occurs, you can improve site performance, especially on pages with a lot of scripts or third-party widgets.

• Implement Lazy Loading with GTM:
  • You can use GTM’s triggers to set up lazy loading of tags. For example, for a social media widget or chat feature that isn’t essential to the first user interaction, set up a Scroll Depth Trigger or Visibility Trigger to load the tag when the user reaches a certain part of the page.
  • Scroll Trigger: If you only want a specific tag (e.g., an analytics event for tracking engagement with a certain section of your site) to load when a user scrolls to that part of the page, create a scroll depth trigger and assign it to the tag.

4. Limit the Number of Tags

Having too many tags running on your site can impact its performance, particularly if those tags include third-party scripts or other resources that add to the page load time.

• Audit and Minimize Tags:
  • Regularly audit your GTM container and remove any unnecessary or redundant tags.
  • Use built-in triggers for more efficient firing (e.g., firing only on the pages where specific tags are needed).
  • For instance, if you have different marketing tools, ensure that tags are only firing when necessary, such as limiting social media pixels or remarketing tags to only fire on key pages (like the checkout page or product pages).

5. Leverage GTM Built-in Variables and Triggers Efficiently

GTM offers a range of built-in variables and triggers that can be configured to fire tags only when necessary, which can help avoid unnecessary tag execution and reduce page load time.

• Optimize Triggers:
  • Instead of triggering tags to fire on every page load, set up more refined triggers. For example:
    • Use Page URL or Page Path to target specific pages where a tag is needed.
    • Use Click Triggers to fire tags only when a user interacts with certain elements (e.g., clicks on a button or submits a form).
    • Use Visibility Triggers to track elements when they become visible on the screen, ensuring you’re not firing unnecessary tags for off-screen elements.
  • This reduces the number of times a tag is fired, which in turn optimizes your site’s loading performance.

6. Implement Event-Driven Tags (Instead of Page Loads)

Rather than firing tags on page load, consider triggering tags based on specific user interactions or events, such as clicks or form submissions. This ensures that tags fire only when they are relevant to the user, which can speed up page load times.

• Event Tracking:
  • Set up custom event triggers in GTM that only fire when the user interacts with a specific element. For example, if you want to track form submissions, set up a trigger for the form submission event and use it to fire tags.
  • Similarly, use Click Triggers to fire events for user clicks rather than having everything load on page load.

7. Use Custom HTML Tags to Minimize JavaScript Execution

If you need to add custom JavaScript to your site, be mindful of how it affects performance. Writing efficient code and avoiding unnecessary execution can help.

• Optimize Custom HTML Tags:
  • Use custom HTML tags in GTM for JavaScript that enhances functionality but may have performance implications. For instance, only include critical scripts in the header or body of the page and defer or load non-essential scripts later.
  • Keep your custom HTML tags lightweight and efficient to reduce execution time.

8. Use Google Tag Manager’s Built-in Performance Tools

GTM includes built-in tools to help monitor the performance of your tags.

• Tag Assistant and GTM Debugger: These tools help you test and troubleshoot tags to ensure they’re firing correctly without causing performance issues. You can use them in Preview Mode to verify that your tags are working as expected before publishing them.

9. Enable AMP (Accelerated Mobile Pages) Support for Tags**

If your website uses AMP, you can still implement GTM to track performance and site interactions without affecting speed.

• Implementing GTM on AMP:
  • AMP pages prioritize performance, so using GTM on AMP requires special considerations. GTM for AMP uses a simplified set of tags to ensure that page load speeds are not impacted. Follow AMP’s best practices when implementing GTM to avoid negatively impacting page performance.

10. Use GTM to Manage Tag Versions and Updates Efficiently

Managing tag updates efficiently ensures that old or outdated scripts do not degrade site performance.

• Version Control: Regularly update your tags and containers in GTM, and use the Versioning feature to roll back to previous versions in case an update negatively impacts performance.

Conclusion

While Google Tag Manager itself doesn’t directly optimize website performance, it plays a critical role in managing how and when tags are fired, which can significantly improve your site’s load time and overall performance. By prioritizing tags, using asynchronous loading, deferring non-essential tags, and leveraging triggers intelligently, you can minimize the impact of tracking tags on site speed. Regular audits of your GTM container and efficient use of custom code and triggers are key to ensuring that your website delivers a fast, seamless experience to users while capturing the necessary data for tracking and analytics.