How to Improve CLS on Mobile Pages: A Step-by-Step Guide
To improve Cumulative Layout Shift (CLS) on mobile pages, optimize images and fonts, reserve space for dynamic content, avoid inserting elements above existing content, and leverage proper CSS and performance best practices.

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Key Takaways






Frequently Asked Questions
What is a good CLS score for mobile?
CLS is part of Google's Core Web Vitals, which influence mobile search rankings and user experience. A low CLS improves engagement and lowers bounce rates.
Why is CLS important for mobile SEO?
CLS is part of Google's Core Web Vitals, which influence mobile search rankings and user experience. A low CLS improves engagement and lowers bounce rates.
Can fonts cause layout shifts on mobile?
Yes, late-loading custom fonts can cause text layout shifts. Preloading fonts and using font-display: swap helps prevent this.
How do ads impact CLS?
Ads often load after content and push elements down. Reserving space for ad containers avoids shifting.
What tools can I use to track CLS?
Use Google PageSpeed Insights, Chrome DevTools Lighthouse, or the Web Vitals extension to track and debug CLS values.
Step by Step Plan
Measure Your Current CLS Score
Use tools like Google PageSpeed Insights or Lighthouse to identify layout shifts and quantify your CLS value. Aim for a score below 0.1 on mobile.
Set Dimensions for Images and Media
Explicitly define width and height attributes for all images, videos, and embeds to reserve space before content loads.
Preload Fonts and Use Font Display Settings
Use font-display: optional or swap in CSS and preload custom fonts to prevent large layout shifts during rendering.
Preload Fonts and Use Font Display Settings
Allocate fixed-size containers for elements like ads, pop-ups, or third-party widgets to reduce unexpected visual jumps.
Avoid Above-the-Fold DOM Manipulation
Prevent layout shifts by minimizing JavaScript-injected elements above existing content, especially during page load.
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