Cumulative Layout Shift: Easy Fixes for WordPress

Cumulative Layout Shift (CLS) is one of the most critical metrics in Google’s Core Web Vitals, designed to measure the visual stability of your website. A high Cumulative Layout Shift score can lead to frustrating experiences for visitors, such as buttons moving just before they are clicked or images suddenly shifting as the page loads. These disruptions create poor usability and negatively impact your search engine rankings. If you’ve noticed unexpected design or content shifts on your WordPress site, it’s likely due to Cumulative Layout Shift issues that need attention.

With the right techniques, it is possible to diagnose and resolve Cumulative Layout Shift problems. By addressing these cumulative layout shifts, you’ll improve your site’s performance, provide a smoother user experience, and increase your chances of ranking higher on Google. In this guide, we’ll walk you through how to identify the causes and fix them effectively, ensuring your website delivers stable, user-friendly browsing every time.

Let’s dive in!

What is Cumulative Layout Shift (CLS)?

Cumulative Layout Shift measures how much visible content shifts unexpectedly during the loading phase of a page. For example, have you ever tried to click a button, but it suddenly moved because an image or ad loaded above it? That’s Cumulative Layout Shift in action.

A good Cumulative Layout Shift score is 0.1 or lower. Anything higher can lead to a poor user experience and reduced rankings in Google.

Common Causes of High CLS in WordPress

Before we resolve the issue, it’s essential to understand what causes CLS on your site:

• Unoptimized Images: Images without defined dimensions can cause layout shifts.
• Ads and Embeds: Dynamic ad slots or embedded content often push content unexpectedly.
• Web Fonts: Poor font-loading strategies may result in a flash of unstyled text (FOUT) or a flash of invisible text (FOIT).
• Lazy Loading Issues: Improper lazy loading of images or iframes can cause elements to jump.
• Dynamic Content: Widgets, animations, or pop-ups loading late can shift elements.

How to Measure CLS on Your WordPress Site

• Google PageSpeed Insights: Analyze your URL and review the CLS score in the Core Web Vitals section.
• Lighthouse in Chrome Developer Tools: Open Chrome DevTools, go to the Performance’ tab and run an audit.
• Web Vitals Extension: Install the Chrome Web Vitals extension to monitor CLS in real time.

Step-by-Step Guide to Fixing CLS in WordPress

1. Set Image Dimensions

Unoptimized images are the leading cause of layout shifts. Here’s how to fix them:

• Use WordPress’s built-in image editor to set width and height attributes for images.
• Add the following CSS for dynamic image resizing:

img {
    max-width: 100%;
    height: auto;
}

• Use plugins like Smush or Imagify to optimize images for size and quality.

2. Reserve Space for Ads and embeds.

For ads and embedded content:

• Use CSS to reserve space for ads, ensuring no unexpected shifts occur.
• Example:

ads..ad-slot {
    min-height: 250px; /* Reserve height for ads */
}

• Follow your ad provider’s guidelines to define fixed dimensions.

3. Optimize Font Loading

Web fonts often cause CLS issues. To fix this:

• Use font-display: Swap in your CSS to load fallback fonts while web fonts load:

@font-face {
    font-family: 'CustomFont';
    src: url('customfont.woff2') format('woff2');
    font-display: swap;
}

• Leverage plugins like OMGF (Optimize My Google Fonts) to preload fonts efficiently.

4. Correct Lazy Loading Issues

Lazy loading can improve performance but must be implemented carefully.

• Ensure critical images (like above-the-fold content) are excluded from lazy loading.
• Add this to your functions.php file to disable lazy loading for key images:

add_filter('wp_lazy_loading_enabled', '__return_false');

5. Preload Key Resources

Preloading critical resources like fonts, images, and CSS ensures they load faster and reduces shifts.

• Add preload tags in your header:

<link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin="anonymous">
<link rel="preload" href="image.jpg" as="image">

• Use plugins like WP Rocket for easy resource preloading.

6. Test Dynamic Content

Widgets, animations, and pop-ups can be a significant source of CLS. Fix them by:

• Reserving space in the layout for widgets.
• Using transition animations sparingly.
• Testing plugins for compatibility and avoiding overly dynamic elements.

Tools and Plugins to Help Fix CLS

• WP Rocket: Includes features to preload resources, optimize fonts, and improve overall performance.
• Smush: Optimizes images and ensures dimensions are set.
• Autoptimize: Combines and minifies CSS, JS, and HTML to enhance loading performance.
• Asset CleanUp: Helps manage and reduce unused CSS and JavaScript.
• OMGF: Optimizes Google Fonts for better loading.

Best Practices to Maintain a Low CLS Score

• Always define dimensions for images, videos, and other media.
• Use lightweight themes that prioritize performance.
• Regularly test your site with tools like PageSpeed Insights.
• Minimize the use of dynamic or third-party content.
• Stay updated with the latest WordPress practices and plugins.

FAQs – Cumulative Layout Shift

Conclusion

Addressing Cumulative Layout Shift in WordPress is essential for creating a smooth and stable browsing experience. By optimizing images, preloading fonts, setting size attributes, and avoiding late-loading elements, you can significantly reduce layout shifts and improve visual stability for your users.

Remember, fixing Cumulative Layout Shift isn’t just about aesthetics; it directly impacts your Core Web Vitals and SEO performance. Start applying these best practices today to enhance both user satisfaction and search rankings.