Reducing Cumulative Layout Shift (CLS) on Your Website
Cumulative Layout Shift (CLS) is a metric used to quantify the visual stability of a website. High CLS scores indicate that the content on your page shifts unexpectedly during loading, which can lead to frustrating user experiences. Reducing CLS is essential for improving user satisfaction and optimizing your site's performance. Below are several strategies to effectively decrease CLS on your website.
1. Prioritize Size Attributes for Images and Videos
One of the main causes of layout shifts is the absence of size attributes for images and videos. Always ensure you declare the width and height of these elements explicitly. This allows the browser to allocate the appropriate amount of space during page load, preventing unexpected shifts.
2. Use CSS for Font Loading
Fonts can sometimes lead to layout shifts, especially if the browser loads them after the rest of the page. Implementing the CSS `font-display` property gives you control over how fonts are rendered. Using `font-display: swap;` allows the browser to show fallback fonts while custom fonts are loading, mitigating layout shifts.
3. Reduce External API Calls
External resources, such as ads or widgets, can load unpredictably, contributing to layout shifts. To minimize this, try to limit the use of dynamic content or ensure that placeholders are used. Define fixed sizes for these external elements to allocate enough space during the initial load.
4. Evaluate Ad Sizes
Advertisements are notorious for causing layout shifts. To keep them from impacting your CLS, use ad sizes that are responsive and include designated space in your layout. This allows your layout to remain stable as ads load. Consider using a placeholder for ads or implementing asynchronous loading to further mitigate shifts.
5. Minimize DOM Changes Post-Load
Avoid late-in-the-load modifications to the DOM, as they can cause elements to move. This could involve scripts that change text or add elements after the initial render. Consider structuring your content to load fully before any dynamic elements are injected, or use techniques to control their visibility until the page has stabilized.
6. Improve Server Response Times
Fast server response times contribute greatly to overall loading speed, which can influence CLS. Optimize your server performance through techniques such as caching, content delivery networks (CDNs), and efficient database queries. By improving response times, you can help your content render more consistently.
7. Regularly Audit Your Website
Conduct regular audits using tools like Google PageSpeed Insights or Lighthouse to identify elements that negatively impact your CLS score. These tools provide valuable insights and specific recommendations that can help you stay ahead of layout shift issues as you update your site.
8. Optimize CSS and JavaScript Loading
Blocking resources can delay the rendering of your page and cause layout shifts. Optimize the loading of CSS and JavaScript by using techniques such as minification, deferring non-critical JavaScript, and using asynchronous loading when possible. These optimizations help ensure that your content appears stable and does not shift unexpectedly.
By implementing these strategies, you can significantly reduce the cumulative layout shift on your website. A lower CLS score not only improves the overall user experience but also enhances your site's search engine rankings, making it a win-win for both users and site owners.