Unexpected movement while a page loads
Cumulative Layout Shift measures the amount of unexpected movement that occurs while a webpage is loading. Google recommends maintaining a CLS score of 0.1 or lower to deliver an excellent page experience.
What layout shifts look like
- • A button suddenly moves before being clicked
- • Images appear without reserved space
- • Advertisements load after the page content
- • Fonts change after the page has rendered
- • Dynamic content pushes existing elements down
Why CLS Optimization Matters
A stable website improves usability and builds trust with visitors. Visual stability plays a significant role in creating professional and user-friendly websites.
What causes poor CLS
Unexpected layout shifts usually occur because website elements are loaded without proper planning.
Images Without Defined Dimensions
Images that load without reserved width and height force surrounding content to move.
Advertisements and Embedded Content
Ads, videos, and embedded widgets often load after the page, causing layout changes.
Dynamic Content
Popups, banners, announcements, and dynamically inserted sections can shift existing content.
Web Fonts
Late-loading fonts may replace fallback fonts and change the size or spacing of text.
Third-Party Widgets
Chat widgets, social feeds, or review tools may introduce unexpected layout changes.
Slow Resource Loading
Delayed loading of CSS, scripts, or media can affect page rendering and stability.
Best Practices for CLS Optimization
Following these optimization techniques helps maintain visual stability across your website.
Reserve Space for Images
Always define width and height so browsers allocate layout space before images load.
Allocate Space for Advertisements
Reserve fixed containers for ads and embedded media to prevent content movement.
Optimize Font Loading
Use modern formats, preload important fonts, and reduce font variations and swapping.
Avoid Injecting Content Above Existing Elements
Load banners and notifications without pushing visible content downward.
CLS Optimization Checklist
Following these steps helps create a smooth and professional browsing experience.
Tools to Measure CLS
Several tools help identify layout shifts and measure visual stability. Regular testing helps identify layout issues before they impact users.
Google PageSpeed Insights
Scores real-world and lab performance against Core Web Vitals thresholds.
Lighthouse
Runs automated audits for performance and best practices.
Google Search Console
Reports Core Web Vitals issues detected across a live site.
Chrome DevTools
Profiles rendering and layout activity in the browser.
GTmetrix
Breaks down load waterfall charts to find what's shifting layout.
WebPageTest
Tests performance from multiple real locations and connection speeds.
Chrome User Experience Report (CrUX)
Shows real-world CLS data collected from actual Chrome users.
Build Fast, Stable, User-Friendly Websites
These resources provide additional strategies for building fast, stable, and user-friendly websites.
How to Build Fast Websites
Foundational principles for performance-first development.
Core Web Vitals Guide
Understand LCP, INP, and CLS and why they matter.
Website Speed Checklist
A 15-point checklist for launching or optimizing a website.
LCP Optimization
Techniques for improving how quickly main content becomes visible.
INP Optimization
Ways to keep a page responsive to clicks, taps, and input.
Image Optimization Services
Reducing image size and format overhead without losing quality.
CDN Optimization
Configuring content delivery networks to shorten data travel.
JavaScript Performance
Minimizing script execution time so pages stay interactive.
Lazy Loading Images
Deferring offscreen media so initial load stays lightweight.
How The Bot Digital Solutions Optimizes CLS
We help businesses improve Cumulative Layout Shift by analyzing website layouts, optimizing media delivery, improving font loading, and implementing modern front-end development practices.
Website Layouts
Analyzing page structure to identify where instability originates.
Media Delivery
Optimizing how images, video, and embeds load into the page.
Font Loading
Reducing swap-related shifts through modern loading strategies.
Front-End Practices
Implementing modern development patterns that reserve layout space.
Cross-Device Testing
Verifying stability across desktop, tablet, and mobile.
Continuous Monitoring
Tracking CLS over time to catch regressions after updates.
Ready for the next step
Ready to Stabilize Your Website's Layout?
Get a CLS assessment and a clear plan to eliminate unexpected layout shifts across your website.
CLS Optimization FAQs
Common questions businesses ask about improving Cumulative Layout Shift.
CLS (Cumulative Layout Shift) is a Core Web Vital that measures how much webpage elements move unexpectedly while a page is loading.
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These services put CLS improvements into practice on a live website.
Put this guide into practice
Start with a CLS assessment
We identify what's causing unexpected layout movement and help you prioritize fixes that improve stability, rankings, and conversions.