Cumulative Layout Shift (CLS) measures how stable your webpage is while it loads.
If buttons, images, or text suddenly move on the screen, visitors can click the wrong thing or lose their place.
These unexpected shifts create a frustrating experience and make your website feel unprofessional.
CLS is also one of Google’s Core Web Vitals, which means it plays a role in search rankings. A poor CLS score can hurt both user experience and SEO performance.
The good news is that CLS problems in WordPress are usually easy to fix once you know what causes them.
In this guide, you’ll learn simple and practical steps to identify layout shifts and fix them to improve your site’s stability and performance.
What is Cumulative Layout Shift (CLS)?
Cumulative Layout Shift (CLS) is a Core Web Vitals metric that measures how much elements on a webpage move unexpectedly while the page is loading.
In simple terms, it tracks visual stability. When text, images, buttons, or ads suddenly shift position on the screen, it creates a poor experience because users may lose their place or accidentally click the wrong thing.
Google measures CLS by calculating how often visible elements move and how far they shift within the viewport during the page load process.
Each unexpected movement receives a score based on the size of the shifting element and the distance it moves, and these scores are combined to create the final CLS value.
A good CLS score is 0.1 or lower, which means the page remains stable as it loads. Higher scores indicate more layout instability and a worse user experience.
Layout shifts usually happen when content loads without reserved space on the page.
For example, an image without a defined width and height may push text downward when it appears, an advertisement might suddenly insert itself above existing content, or a web font might load late and change the size of the text.
Another common case is when a button moves just as someone tries to click it, causing them to click something else instead.
These shifts can feel small, but they quickly frustrate visitors and reduce trust in your website.
Why CLS Happens in WordPress
Images Without Defined Dimensions
Images are one of the most common causes of layout shifts in WordPress.
When an image is added to a page without specifying its width and height, the browser does not know how much space to reserve for it while the page loads.
As a result, the browser first loads the surrounding text and layout, then later pushes that content down when the image finally appears.
This sudden movement creates a layout shift that increases your CLS score.
Modern versions of WordPress usually add image dimensions automatically, but problems still happen when images are inserted through page builders, custom HTML blocks, or third-party plugins that remove these attributes.
The simple solution is to always ensure images include proper width and height values or use responsive image containers that preserve the correct aspect ratio before the image loads.
Ads, Embeds, and Iframes Loading Late
Third-party content such as advertisements, YouTube videos, social media embeds, and other iframes can also trigger layout shifts.
These elements often load after the main page content because they rely on external scripts.
When the browser finally receives the content, it inserts the element into the page and pushes surrounding content up or down.
This is especially common with ad networks that dynamically insert ads into available spaces on a page.
If there is no reserved container for the ad or embed, the page layout will shift once the content appears.
The best way to prevent this issue is to create fixed containers for ads and embedded content so the browser reserves space for them before they load.
Fonts Causing Layout Shifts (FOIT/FOUT)
Web fonts can also cause layout instability if they are not loaded properly.
When a page uses custom fonts from services like Google Fonts, the browser may initially display fallback fonts until the custom font finishes loading.
This behavior is known as Flash of Invisible Text (FOIT) or Flash of Unstyled Text (FOUT).
Once the custom font loads, the text may change size or spacing, which causes other elements on the page to shift.
Even small changes in font width can push lines of text onto new rows and move buttons or images below them.
To reduce this problem, fonts should be optimized using proper loading strategies such as font preloading and the font-display: swap property, so the layout remains stable while fonts load.
Dynamic Content and Lazy Loading Issues
Dynamic elements can also introduce layout shifts when they appear after the initial page render.
Examples include cookie banners, popups, newsletter sign-up forms, related post sections, or content that loads through JavaScript.
Lazy loading can also cause shifts if images or videos appear without reserved space.
When these elements suddenly appear above existing content, the entire page moves downward, creating a poor user experience.
This often happens when banners or notification bars are inserted at the top of a page after it has already started loading.
To prevent this, dynamic content should either reserve space in advance or load in areas that do not push other content out of position.
Poorly Optimized Themes and Plugins
Some WordPress themes and plugins are not built with performance and layout stability in mind.
Poorly coded themes may load scripts that modify the layout after the page has already rendered.
Plugins can also inject elements such as banners, widgets, or scripts that change the page structure unexpectedly.
Page builders sometimes generate complex layouts that rely heavily on JavaScript, which increases the risk of layout shifts during loading.
In addition, plugins that insert ads, review boxes, affiliate banners, or recommendation widgets may add content dynamically without reserving space for it.
Choosing well-optimized themes and limiting unnecessary plugins helps reduce these risks and keeps your page layout stable.
How to Check CLS on Your WordPress Website
- Using Google PageSpeed Insights
Google PageSpeed Insights analyzes your webpage and reports Core Web Vitals, including CLS. Simply enter your website URL and run the test. The tool shows your CLS score, highlights the elements causing layout shifts, and provides suggestions to improve stability. - Using Google Search Console Core Web Vitals Report
Google Search Console provides real-world performance data collected from actual users. In the Core Web Vitals report, you can see which pages on your website have poor CLS scores. This helps you identify layout shift issues across your entire site instead of testing one page at a time. - Using Lighthouse in Chrome DevTools
Lighthouse is built into the Chrome browser and allows you to run a detailed performance audit directly from your browser. Open your website, launch Chrome DevTools, and run a Lighthouse report. The results include your CLS score and highlight the specific elements that shift during page load. - Using GTmetrix
GTmetrix provides a detailed performance analysis that includes CLS measurements. After entering your website URL, the tool generates a report showing layout shift events, performance metrics, and recommendations for improving page stability.
How to Fix Cumulative Layout Shift (CLS) in WordPress
Set Image Width and Height Attributes
Images should always include defined width and height values so the browser knows how much space to reserve before the image loads.
Without these dimensions, the browser initially loads surrounding text and layout elements, then pushes them down once the image appears.
This creates a noticeable layout shift that increases your CLS score.
When image dimensions are defined, the browser allocates the correct space immediately, preventing movement during loading.
Modern versions of WordPress usually add width and height attributes automatically when images are inserted through the media library.
However, problems can still occur when images are added through custom HTML blocks, page builders, or third-party plugins that remove these attributes.
To avoid CLS issues, always upload images through the WordPress media library or ensure your page builder maintains proper image dimensions.
Using responsive images with preserved aspect ratios also helps keep layouts stable across different screen sizes.
Reserve Space for Ads and Embeds
Advertisements, videos, and embedded content often load after the main page content because they rely on external servers.
If no space is reserved for them, they suddenly appear and push existing content downward. This is one of the most common causes of CLS on content-heavy websites.
To prevent this problem, create dedicated containers that reserve space for ads and embeds before they load.
For example, you can set fixed-height containers for banner ads or video embeds so the layout remains stable even while the content is still loading.
This ensures that when the ad or embedded content appears, it fills the reserved space instead of shifting other elements on the page.
Optimize Web Fonts
Web fonts can cause layout shifts when the browser first displays fallback fonts and later replaces them with custom fonts.
This change can alter the spacing and size of text, which moves other elements on the page. To reduce this issue, implement proper font loading strategies.
One effective method is using font-display: swap, which allows the browser to show fallback text immediately and then replace it smoothly once the custom font loads.
Preloading important fonts can also improve stability by instructing the browser to load them earlier in the page loading process.
When fonts load faster and more predictably, text rendering becomes more stable, and CLS is reduced.
Avoid Inserting Content Above Existing Content
Content that appears above already loaded elements can cause major layout shifts.
This often happens with cookie notices, promotional banners, announcement bars, or popups that are injected at the top of the page after the page begins loading.
When this new content appears, it pushes everything else downward, creating a sudden visual jump.
A better approach is to reserve space for these elements or position them in a way that does not move existing content.
For example, cookie banners can be placed as overlays instead of pushing page content down.
Dynamic content should always be designed so that it does not interrupt the existing layout once users begin interacting with the page.
Use Proper Lazy Loading
Lazy loading improves performance by loading images and videos only when they are about to appear on the screen.
However, if it is implemented incorrectly, it can cause layout shifts.
This happens when the browser does not know the size of the image before it loads, leaving empty space that changes once the image appears.
To prevent this, always combine lazy loading with defined image dimensions or aspect ratio containers. This ensures the browser reserves the correct space before the image loads.
When implemented correctly, lazy loading improves page speed without causing elements to shift during scrolling.
Preload Important Resources
Preloading helps the browser prioritize critical resources needed for the initial layout of the page.
Important elements such as hero images, primary fonts, and key style files should load early so the browser can build a stable layout from the beginning.
Without preloading, these resources may load later in the process, causing elements to appear or resize after the page has already started rendering.
Preloading important assets ensures that key visual components are available when the browser first constructs the layout.
This reduces the chances of late-loading elements shifting the page.
Reduce Third-Party Scripts
Third-party scripts can introduce layout instability because they often inject content dynamically after the page loads.
Examples include ad networks, analytics tools, social media widgets, and recommendation engines.
These scripts can insert elements that alter the layout unexpectedly, which increases CLS.
The best way to manage this is to limit unnecessary third-party scripts and carefully evaluate the ones you use.
Scripts that must remain on the site should load efficiently and reserve space for any content they inject.
Reducing script dependencies and loading them strategically helps keep your page layout stable and improves overall performance.
Best WordPress Plugins to Fix CLS
Fixing Cumulative Layout Shift often becomes easier when you use the right performance plugins.
These tools help control how images, scripts, fonts, and other elements load on your website. Below are the main categories of plugins that can help reduce CLS in WordPress.
Caching and Performance Plugins
These plugins improve how your website loads by optimizing page delivery, reducing render delays, and controlling resource loading.
Many of them also include features that help stabilize page layout.
- WP Rocket – A premium performance plugin that improves loading behavior through page caching, file optimization, and delayed JavaScript execution. It also helps prevent layout shifts by optimizing how CSS and scripts load.
- LiteSpeed Cache – A powerful optimization plugin designed for LiteSpeed servers. It includes page caching, image optimization, and CSS/JavaScript controls that can help reduce CLS issues.
- W3 Total Cache – A comprehensive caching plugin that improves server response times and resource loading, helping pages render more smoothly.
Image Optimization Plugins
Images are one of the most common causes of layout shifts. Image optimization plugins help manage image sizes, compression, and loading behavior to keep layouts stable.
- ShortPixel – Compresses and optimizes images without reducing visual quality. Smaller images load faster and reduce the chances of late content shifts.
- Smush – Automatically compresses images and ensures they are served in optimized formats while maintaining proper dimensions.
- Imagify – Optimizes images and supports modern formats like WebP, helping images load efficiently and reducing layout disruptions.
Asset Optimization Plugins
Asset optimization plugins manage how CSS, JavaScript, and other resources load on your site.
- Perfmatters – A lightweight performance plugin that allows you to disable unnecessary scripts, optimize font loading, and reduce layout shifts caused by third-party resources.
- Asset CleanUp – Lets you remove unused CSS and JavaScript from specific pages, reducing unnecessary scripts that could interfere with page layout.
- Autoptimize – Aggregates and optimizes CSS and JavaScript files, helping pages load more efficiently and reducing unexpected layout shifts.
Using one or two well-configured performance plugins is usually enough to address most CLS problems.
Installing too many optimization plugins can create conflicts, so choose tools carefully and test your website’s performance after making changes.
Best Practices to Prevent CLS in the Future
Use Properly Coded Themes
Your WordPress theme plays a major role in how stable your website layout is. A well-coded theme follows modern web standards and loads elements in a predictable way.
Poorly coded themes often rely on heavy scripts, dynamic elements, or poorly structured layouts that can shift during page loading.
When choosing a theme, prioritize lightweight themes that are built with performance in mind.
Reliable themes usually define image sizes correctly, manage fonts properly, and avoid injecting elements that change the layout after the page begins rendering.
Before installing a new theme, review its performance reputation and test it on a staging site whenever possible.
Test Layout Changes Before Publishing
Layout shifts often appear after design changes, plugin updates, or new content elements are added to a page.
For example, adding a banner, embedding a video, or inserting a new plugin widget can change how the page loads.
Testing these changes before publishing helps you catch layout issues early. Use tools such as PageSpeed Insights or Lighthouse to review your page after making updates.
Pay close attention to how images, fonts, ads, and dynamic content behave during loading.
If any element pushes other content out of place, adjust the layout by reserving space or defining proper dimensions before making the page live.
Monitor Core Web Vitals Regularly
Website performance should be monitored continuously rather than checked once and forgotten.
Core Web Vitals reports help you track CLS and other important performance metrics over time.
Google Search Console provides real-world data from visitors and shows which pages are experiencing layout instability.
Reviewing this report regularly helps you detect new CLS problems caused by updates, plugins, or design changes.
Monitoring performance allows you to respond quickly and keep your site stable for users.
Optimize Images and Fonts
Images and fonts are two of the most common sources of layout shifts, so managing them properly is essential.
Always upload properly sized images and ensure they include width and height attributes so the browser reserves the correct space during loading.
Large images should be compressed to reduce loading delays.
Fonts should also be optimized so they load quickly and do not change the layout after the page begins rendering.
Using efficient font loading strategies and limiting the number of font variations can significantly reduce visual instability.
When images and fonts are handled correctly, your pages load smoothly and maintain a stable layout for visitors.
Final Thoughts
Fixing Cumulative Layout Shift makes your website easier to use and more reliable for visitors.
A stable page layout prevents frustrating jumps, improves user experience, and helps build trust with your audience.
It also strengthens your Core Web Vitals, which can support better search engine rankings.
Make performance testing a regular habit. Check your CLS score after updates, design changes, or new plugins to ensure your pages remain stable and fast.
Small adjustments over time can keep your WordPress site smooth, professional, and optimized for both users and search engines.
FAQs
What is a good CLS score?
A good CLS score is 0.1 or lower. Scores between 0.1 and 0.25 need improvement, while anything above 0.25 is considered poor.
Does CLS affect SEO rankings?
Yes. CLS is part of Core Web Vitals, which Google uses as a ranking factor. A poor CLS score can negatively impact both user experience and search performance.
How do I check CLS in WordPress?
You can check CLS using tools like Google PageSpeed Insights, Google Search Console, Lighthouse, or GTmetrix.
These tools show your CLS score and highlight the elements causing layout shifts.
Can plugins cause CLS issues?
Yes. Some plugins add dynamic elements, ads, or scripts that load after the page begins rendering. If they do not reserve space for these elements, layout shifts can occur.
How long does it take to fix CLS problems?
Most CLS issues can be fixed quickly once the cause is identified.
Simple fixes like defining image sizes or reserving space for ads can often resolve the problem in minutes.