As the digital landscape evolves, user experience (UX) becomes more crucial than ever. One key metric that plays a significant role in UX is the Cumulative Layout Shift (CLS) score. In 2025, the importance of optimizing the CLS score is more pronounced than ever for businesses and web developers aiming to enhance their websites’ performance. This article will explore the CLS score, its importance, and how it impacts website optimization.
What is the CLS Score?
The CLS score is one of the Core Web Vitals, a set of metrics developed by Google to measure website performance. Specifically, CLS measures the visual stability of a webpage as it loads. It tracks how much the page layout shifts during loading and how often this causes users to interact with the page unintentionally.
A high CLS score means that the layout of your page is shifting around during loading, which can be annoying and frustrating to users. This can lead to unintended clicks, difficulty reading content, and even users leaving your page due to the poor experience.
Why is CLS Score Important?
The CLS score has a direct impact on the user experience. A page with a high CLS score can negatively affect your website’s usability. Users may have trouble interacting with the site because content keeps shifting. A poor user experience leads to higher bounce rates, and lower engagement, and can ultimately harm your website’s SEO ranking.
Google uses CLS as a ranking factor in its search algorithm. This means that pages with poor visual stability may rank lower on search engine results, affecting organic traffic and visibility. In other words, improving your CLS score not only improves user experience but also helps with SEO performance.
Understanding How CLS Affects User Experience
User experience (UX) is everything. Users expect websites to be fast, responsive, and easy to interact with. When elements on a page shift unexpectedly, it disrupts the user’s ability to interact with content and can even cause them to click on the wrong link or button. This frustration leads to poor engagement and reduced satisfaction.
A website with a high CLS score can feel unpredictable and unstable. For example, if you are reading an article, but the text moves around while the page loads, it can be difficult to focus on the content. This not only makes the website harder to use but can also cause users to leave your site before the page fully loads.
Google’s Core Web Vitals, which include the CLS score, have become significant ranking factors. Websites with poor CLS scores are less likely to rank well on search engines, potentially resulting in lost visitors and lower conversions.
What is a Good CLS Score?
A good CLS score is below 0.1. This means that the layout shift during loading is minimal and hardly noticeable to users. A score below 0.1 indicates that the page has excellent visual stability. If your CLS score is between 0.1 and 0.25, it is considered acceptable, but improvements should be made. A score above 0.25 is considered poor and should be addressed immediately.
In 2025, optimizing for a low CLS score should be a priority for businesses and developers who want to provide a top-tier user experience and maintain strong search engine rankings.
How to Improve Your CLS Score
Improving your CLS score is crucial for optimizing your website. There are several ways to improve the visual stability of your website and reduce layout shifts during loading.
Here are some tips on how to improve your CLS score:
1. Set Size for Images and Videos
Always define width and height attributes for images and videos in your CSS. This ensures that space is reserved for the media content before it loads, preventing unexpected shifts in the layout. This is particularly important for larger images or videos.
2. Use Proper Font Loading Techniques
Fonts are another common source of layout shifts. If a font is not loaded correctly, the text may shift when it eventually appears. Implement font-display strategies like font-display: swap to ensure text is visible even before the font loads.
3. Avoid Dynamic Content Shifts
Sometimes, dynamic content such as ads or popups can load after the page has started rendering. These elements may push other content around, causing layout shifts. Use placeholders for dynamic content so that the space is already reserved before it loads.
4. Minimize the Use of Web Fonts
Web fonts, especially when used improperly, can increase CLS. If fonts take too long to load or render incorrectly, they cause shifts. Minimize the number of web fonts used and make sure to load them in an optimized way.
5. Implement Lazy Loading for Images
Lazy loading allows you to load images only when they appear in the user’s viewport. This technique reduces the number of images that need to be loaded initially, which in turn reduces layout shifts caused by images loading at different times.
6. Use Stable Layouts for Interactive Elements
Interactive elements such as buttons, menus, and links should have stable layouts that do not shift unexpectedly. Ensure that these elements have a fixed height and width to avoid movement during loading.
7. Test and Monitor Regularly
Regularly test your website’s CLS score using tools like Google PageSpeed Insights or Lighthouse. Monitoring your website’s performance helps you identify areas for improvement and ensures that your CLS score remains optimized over time.
Tools to Monitor CLS Score
There are several tools available to help monitor and improve your CLS score:
- Google PageSpeed Insights: This tool provides a comprehensive report of your website’s performance, including the CLS score. It also offers suggestions for improvement.
- Lighthouse: A developer tool integrated into Chrome that provides detailed performance audits, including CLS.
- Web Vitals Extension: Google offers a Web Vitals extension for Chrome that helps you measure Core Web Vitals, including CLS, in real-time.
- Chrome DevTools: Use the Chrome DevTools Performance Panel to track CLS during page load and troubleshoot layout shifts.
Conclusion
In 2025, optimizing the CLS score is a key part of improving user experience and SEO. A stable and responsive webpage is critical for keeping users engaged and satisfied. Layout shifts during loading can result in frustration, reduced interaction, and lower search rankings. By improving your CLS score, you can ensure that your website is visually stable, easy to use, and ranks well on search engines.
To improve your CLS score, focus on optimizing images, videos, fonts, and interactive elements. Regular testing and monitoring using tools like PageSpeed Insights and Lighthouse will help you maintain a positive user experience and stay ahead in 2025’s competitive digital landscape.
FAQs
Q1: What is CLS and why is it important?
CLS (Cumulative Layout Shift) measures how much your website’s content shifts during loading. It is crucial because it affects the user experience. A high CLS score means the page layout is unstable, which can frustrate users.
Q2: What is a good CLS score?
A good CLS score is below 0.1. This means minimal layout shifts during page loading, resulting in a better user experience.
Q3: How do I test my CLS score?
You can test your CLS score using tools like Google PageSpeed Insights, Lighthouse, or the Web Vitals Chrome extension.
Q4: How can I improve my CLS score?
You can improve your CLS score by optimizing images and videos, using proper font loading techniques, and avoiding dynamic content shifts.
Q5: How does CLS affect SEO?
A high CLS score can negatively impact SEO because Google uses Core Web Vitals as ranking factors. Pages with poor CLS scores may rank lower on search engines.
