4/13/2025

Troubleshooting Poor Cumulative Layout Shift on Shopify Sites

Cumulative Layout Shift (CLS) is a fundamental metric in web performance that evaluates the visual stability of your website. It's especially critical for Shopify sites, where user experience directly influences conversion rates. When CLS scores are high, it typically means that elements on your page shift or change position while a user is trying to interact with your content, resulting in frustration and potentially leading to higher bounce rates. In this blog post, we’ll explore common causes of poor CLS and give you actionable tips on troubleshooting and optimizing your Shopify store for better performance.

What is Cumulative Layout Shift?

Cumulative Layout Shift is a score that quantifies how often visible elements on a webpage move unexpectedly. Google uses this metric to judge the quality of a page’s user experience. It's part of the Core Web Vitals that determines how well your site performs in terms of loading speed, responsiveness, and visual stability. A high CLS score indicates a poor user experience, meaning visitors could lose their place as they engage with the content—think of it as reading a book and having the pages shift mid-sentence. Not ideal, right?

Why is CLS Important?

High CLS scores can lead to frustrated users, which means they might leave your site without completing their purchase. This is particularly detrimental for eCommerce websites like Shopify, where every moment counts. Common scenarios leading to high CLS include:

Images loading without specified dimensions, causing content to shift down once they appear.
Third-party ads that pop up and push content around unexpectedly.
Late-arriving CSS that disrupts your layout.

By addressing these issues, you can improve your site’s CLS score, enhance user experience, and boost conversion rates.

Common Causes of Poor CLS on Shopify Sites

Let’s dive into the common culprits behind poor CLS scores on Shopify sites:

1. Not Saving Space for Images

One of the most frequent issues is that images lack defined dimensions. When the browser renders a page, it has no clue about the image sizes until they actually load, leading to shifts. To fix this:

Ensure you set the
1height
and
1width
attributes in your
1<img>
tags.
If you're using custom CSS, consider using the
1aspect-ratio
property.
For optimal results, the easiest method is to utilize Liquid’s
1image_tag
. It will automatically add dimensions to your images in the HTML:
1 2html <img src="example.jpg" height="200" width="300" />

This will reserve space before the images load, minimizing layout shifts!

2. Not Saving Space for Injected Content

Shopify stores often utilize third-party apps to enhance functionality, but many of these do not reserve space for injected content, leading to layout shifts. When these elements load via JavaScript, everything below it can shift downward. Solutions include:

Set minimum heights for injected content. For example:
1 2css .shopify-app-block { min-height: 30px; }
If you're using a custom app that injects content in a way that can’t be controlled, be proactive by positioning it carefully in your layout, keeping in mind that injected content should not push essential interaction elements below the fold.

3. Late-Arriving CSS

Using lazy loading for CSS can also impact your CLS. When critical CSS loads asynchronously, the browser may render unstyled elements, leading to layout shifts. Avoid lazy loading for any CSS required above the fold. Instead:

Keep your CSS links in your HTML in a straightforward manner:
1 2html <link rel="stylesheet" href="styles.css">
Consider splitting your CSS files for different sections of your site while ensuring the above-the-fold content is styled promptly.

4. Incorrect Animations

Animations that shift elements by altering their positioning can also inflate your CLS score. If you’re using animations for pop-ups, consider utilizing CSS transforms:

Instead of animating
1top
or
1bottom
properties, use
1transform: translateY()
to animate elements without shifting the layout.

1
2
3
4
.popup {
    animation: popup 0.5s ease;
    transform: translateY(-100%);
}

This method will ensure a smoother animation that is hardware-accelerated and generally more performant.

5. Font Swapping Issues

Web fonts can create large CLS scores when fallback fonts aren’t aligned properly. When your custom font loads, it can change the text layout and line height. To minimize this:

Use better fallback fonts that closely match the appearance of your primary font.
Consider using CSS
1font-display
property to control the font loading behavior.

1
2
3
4
5
@font-face {
    font-family: 'YourFont';
    src: url('yourfont.woff2') format('woff2');
    font-display: swap;
}

This ensures that text is visible during loading instead of being hidden until the web font is loaded.

Measured Tools to Detect CLS

To detect layout shifts and properly diagnose your CLS issues, there are several useful tools available:

1. Google PageSpeed Insights

Using PageSpeed Insights gives you an extensive view of your CLS and overall site performance. The tool highlights specific elements causing layout shifts and suggests improvements.

2. Web Vitals Chrome Extension

Web Vitals is a simple yet powerful Chrome extension that provides real-time feedback about your site's performance directly in the browser console.

3. Chrome DevTools

Use Chrome's built-in DevTools and the Performance tab to record page loads and inspect layout shifts during loading.

Open DevTools > Performance panel > click Record > refresh your page and inspect the timeline for visual shifts that occurred during loading.

Conclusion

Troubleshooting poor CLS on your Shopify site may seem daunting at first, but you can tackle it step by step. By ensuring you have defined dimensions for images, managing injected content, avoiding unnecessary lazy loading for CSS, optimizing animations, and addressing font swapping, you can significantly enhance your site’s user experience. This, in turn, should lead to lower bounce rates and higher conversions.

And don't forget about Arsturn! It offers a fantastic platform for creating custom chatbots that can engage your audience and provide information instantly, helping reduce frustration when users have questions. With Arsturn, you can connect with your audience in meaningful ways, creating a more engaging online shopping experience. What are you waiting for? Tap into the power of conversational AI today!

Improving CLS is a journey, but with the right methods and tools at your disposal, you are well on your way to creating a stable and enjoyable experience for your Shopify visitors!