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Google Tag Manager strategies to minimize impact on website performance and SEO
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In the world of web performance and SEO, efficiency plays a crucial role. Google Tag Manager (GTM) is an invaluable tool for managing tracking codes and third-party scripts, but if not optimized, it can slow down your site. The key is to enhance the performance of GTM itself to reduce its effect on overall website speed and user experience.
This guide outlines strategies to streamline Google Tag Manager, ensuring that it operates efficiently without hindering your site’s performance or SEO.
Why Google Tag Manager optimization is important
Google Tag Manager (GTM) streamlines the process of adding and managing website tags, eliminating the need for manual code updates. It’s an ideal solution for marketers and analysts to update tracking, set up A/B tests, or deploy third-party scripts efficiently, without relying on developers.
Most common use cases for GTM
Why businesses use GTM
Did you know that 48.6% of all websites rely on Google Tag Manager (GTM) to streamline their tag management and GTM holds a 99.7% market share in the category? This popularity is driven by the tool’s business benefits.
GTM eliminates the need for manual code changes, allowing businesses to deploy marketing and analytics tags quickly and without developer involvement. This saves time and accelerates campaigns.
With built-in version control, you can easily track changes and roll back to previous versions when needed. GTM also offers flexibility through conditional triggers - for example, firing a tag only when a specific action occurs, like a purchase.
Consider a Shopify store aiming to implement a new marketing campaign. With GTM, the marketing team can independently add tracking tags to monitor campaign performance, without waiting for developer assistance. This streamlined process accelerates deployment and ensures accurate data collection, facilitating timely adjustments to marketing strategies.
How GTM works and why it can affect performance
GTM works by adding a small script to your site’s HTML, which then loads and manages other scripts in the background. This setup reduces the need for manual code changes, making tag management more efficient. However, if too many tags are added or existing ones aren’t optimized, multiple scripts can run simultaneously in the background. This increases the load on your site’s main thread, potentially slowing down page speed and impacting overall performance.
Potential performance issues:
LCP (Largest Contentful Paint): An overload of tags can delay the loading of essential visual elements, such as images or headlines, causing slower perceived load times.
CLS (Cumulative Layout Shift): Tags that dynamically modify the page after it loads can lead to unexpected layout shifts, frustrating users.
INP (Interaction to Next Paint): Inefficiently processed tags that handle user interactions can result in noticeable lag, diminishing the responsiveness of your site.
By optimizing GTM, you mitigate these risks and ensure faster, more efficient page loads, enhancing both user experience and SEO rankings.
Strategies to optimize Google Tag Manager
1. Audit and remove unnecessary tags and vendors
Over time, your GTM container can accumulate tracking codes and scripts that you no longer need - like that Facebook Pixel you added for a one-time ad campaign or an analytics tag for a discontinued service. These unused or outdated tags can quietly slow down your site.
How to do it:
1. Open Google Tag Manager and go to Tags.
2. Review each tag and ask, "Do I still need this?" If the answer is no, or you’re not sure, pause the tag or delete it.
3. Use GTM’s Preview mode to see which tags fire on different pages and remove duplicates or irrelevant scripts.
Think of it like this: Imagine GTM as a toolbox. If you keep piling in old tools you never use, finding the right one when you need it becomes harder. A clutter-free GTM container makes your website faster and more efficient.
2. Load tags based on importance and timing
Not all tags on your website need to load at the same time. The key is to focus on loading critical tags, like Google Analytics, right away while delaying non-essential ones, such as remarketing pixels, until after your main content is visible. This ensures your site runs smoothly, prioritizing what matters most to your visitors without sacrificing valuable data collection.
How to identify critical vs non-critical tags:
Critical tags: These are the essential scripts that support your site’s core functionality or collect vital data. For example:
Google Analytics for tracking visitor behavior.
Consent Management tools to stay compliant with privacy laws.
E-commerce tracking to attribute revenue accurately.
Non-critical tags: These add value but do not directly impact the initial user experience. For instance:
Remarketing pixels like Facebook or LinkedIn ads.
Heatmaps such as Hotjar for user behavior insights.
A/B testing tools that aren’t tied to the initial layout.
Checklist: deciding how to prioritize your tags
❓Does this tag delay content from appearing on the page?
If it does, think about postponing it to keep your site fast.
❓Does this tag directly drive revenue or improve the user experience?
If so, it’s important to load it right away.
❓Does this script impact how your site looks or feels to visitors?
If yes, prioritize it. If it only collects data, it can be delayed.
Imagine running a Shopify store. By loading your Google Analytics and e-commerce tracking tags first, you ensure you’re capturing sales data while letting non-essential tools like remarketing pixels load later. This keeps your site fast while still collecting the insights you need.
How to implement in GTM:
1. Open Google Tag Manager and find the tag you want to adjust (e.g., a Google Ads pixel).
2. Switch its trigger from the default “Page View” to “Window Loaded,” so it fires after all content has loaded.
3. Alternatively, set up a custom trigger, like a timer or an event tied to a specific part of the page, such as a visible call-to-action.
4. Test your changes in GTM’s Preview mode to make sure everything works as expected.
By managing tag sequencing, you ensure that user experience is prioritized, while still capturing valuable data without impacting performance.
3. Implement page-specific tag firing
To make your site faster and more efficient, fire tags only on the pages where they’re truly needed. Instead of letting every tag load on every page, you can fine-tune your setup to ensure they’re triggered only in the right places or during specific actions.
Why this matters
Limiting tags to relevant pages means your site deals with fewer scripts, speeding up load times and improving the user experience. It also makes your analytics more accurate by ensuring data is collected in the right context, without clutter or irrelevant signals. Plus, when your pages aren’t competing for resources, key performance metrics like Largest Contentful Paint (LCP) and Interaction to Next Paint (INP) see noticeable improvements.
Imagine you have a remarketing pixel aimed at re-engaging users who abandon their carts. Instead of running this pixel across your entire site, set it to fire only on the cart and checkout pages. This way, your informational or blog pages stay lightweight and fast while still capturing valuable cart activity data.
How to do it in GTM
1. Open Google Tag Manager and locate the tag you want to refine.
2. In the Triggers section, replace the default 'All Pages' trigger with a new page-specific trigger.
3. Choose Page Path or Page URL as the condition to specify which pages the tag should fire on.
4. Alternatively, use Click or Form Submission triggers to load tags only after users interact with specific elements (e.g., submit a form, click a button).
5. Test the configuration in Preview Mode to ensure the tag fires correctly only on the designated pages.
4. Avoid excessive DOM manipulation
Tags that involve heavy DOM manipulation can slow down your site and impact the user experience. This happens when the scripts make frequent or complex changes to your web page, like adding large blocks of HTML or modifying several elements at the same time. These processes can delay how quickly the page loads and responds to user actions, making the experience feel sluggish.
For example, a heatmap script like Hotjar or Crazy Egg may dynamically inject large amounts of HTML and JavaScript to visualize user interactions. If this tag loads before your main content, it can delay the rendering of critical elements like a product image or call-to-action button, leading to a slower page load and a frustrating user experience. To avoid this, you can configure such tags to load after the primary content has finished rendering.
Checklist: identifying tags with heavy DOM manipulation:
❓Does the tag use custom JavaScript?
Check if the tag contains large JavaScript blocks that modify page elements, such as injecting banners or pop-ups.
❓Does the tag keep making changes after the page loads?
Some tags, like live chat widgets or dynamic content tools, keep updating your site in the background, which can slow things down.
❓Have you checked if the tag affects site performance?
Use the 'Performance' tab in Chrome DevTools to identify long 'Layout' or 'Recalculate Style' events caused by scripts running through GTM.
5. Use server-side tagging to reduce browser overhead
Server-side tagging shifts the work of running scripts from your visitors' browsers to your server, making your site faster and more secure. Instead of loading lots of third-party scripts directly in the browser, Google Tag Manager (GTM) sends one streamlined request to a server. The server then processes the data and forwards it to marketing tools like Google Ads or Facebook.
Why it matters
With fewer scripts running directly in the browser, server-side tagging allows your site to load faster, significantly improving key metrics like Largest Contentful Paint. It also enhances privacy by processing sensitive data on your server, minimizing exposure to third-party platforms. Additionally, server-side tagging gives you greater control over your data, enabling you to clean, filter, and refine it before sending it to analytics or advertising platforms, ensuring both accuracy and quality.
For example, instead of embedding multiple tracking pixels on your site, you send one request to your server-side GTM container. This container processes the request and forwards the relevant data to Google Ads, Facebook, or any other platform.
How to implement server-side tagging
To implement server-side tagging, set up a GTM server container in Google Cloud or another cloud provider, configure data streams from the website, and route tags through the server. This offloads browser processing, resulting in faster, smoother user experiences.
By offloading the heavy lifting to your server, server-side tagging improves speed, enhances user experience, and ensures that your site runs smoothly - even as your marketing tools work hard behind the scenes.
6. Apply asynchronous loading
Make sure GTM and third-party tags load in the background, so they don’t interrupt or slow down the main content of your site. This way, the important parts of your site (like images and text) load first, while tracking and marketing tags finish loading quietly afterward.
Why it’s important:
When tags load asynchronously, your website feels faster, providing a better experience for visitors. This approach ensures key content is immediately available, allowing users to interact with your site without delays.
For example, tools like Google Analytics can be set to load in the background, ensuring they don’t block the important parts of your page. The result? A smoother, more enjoyable browsing experience for your visitors.
<script async src="https://www.googletagmanager.com/gtm.js?id=GTM-XXXX"></script>
Monitoring GTM performance
After every GTM update, it's crucial to test page speed to evaluate the impact of new tags or triggers. This practice helps catch unintended performance issues early. Use tools like Lighthouse, PageSpeed Insights, and webpagetest.org to measure experiences in a simulated environment and verify improvements in page load times.
Continuous optimization of GTM performance is essential. While tools like Google PageSpeed Insights and Lighthouse offer valuable insights, they primarily reflect lab data and synthetic testing. To gain a deeper understanding of GTM's impact in real-world conditions, prioritize Real User Monitoring (RUM). RUM tracks actual user experiences, measuring how GTM affects load times across different devices, locations, and network conditions. This data reveals performance bottlenecks that synthetic tools might overlook, providing a more accurate view of GTM behavior in the wild. Additionally, monitor tag activity and disable underperforming or unnecessary scripts based on real user data to ensure GTM has minimal impact on performance at scale.
Conclusion
Optimizing Google Tag Manager is key to reducing its impact on website performance and SEO. By eliminating redundant tags, loading scripts asynchronously, and applying targeted triggers, GTM can operate seamlessly without slowing down your site.
At Uxify, we leverage Navigation AI, an AI-driven implementation of the Speculation Rules API for prerendering and prefetching. This predictive technology allows resources - such as GTM scripts - to be preloaded securely before the user reaches the page, preventing blocking of the main thread. As a result, critical scripts load efficiently, ensuring seamless performance without compromising user experience or site speed.
Ready to take your website performance to the next level? Let’s integrate Navigation AI to ensure your GTM setup works flawlessly.
Vasil Dachev
Performance Engineer
Vasil combines his background as a software developer with a talent for solving complex performance challenges. At Uxify, he’s dedicated to breaking down intricate web performance issues into simple, actionable solutions, ensuring every client gets the best results. With Vasil on your side, achieving a faster, smoother website experience is always within reach.