Definition
A Core Web Vitals metric measuring the visual stability of a page by quantifying unexpected layout shifts.
Cumulative Layout Shift (CLS) is one of Google's three Core Web Vitals metrics. It measures the visual stability of a page by calculating the sum of layout shift scores that occur throughout the page's lifespan. A good CLS score is below 0.1. Common causes of high CLS include images without dimensions, dynamic ads, web fonts, and dynamically injected content.
CLS
Cumulative Layout Shift
Key Points
- A good CLS score is below 0.1
- Always set width and height on images and videos
- Reserve space for ads with fixed containers
- Use font-display: swap with preload for web fonts
Practical Examples
Frequently Asked Questions
Use PageSpeed Insights, Lighthouse, Chrome DevTools, or the Core Web Vitals report in Google Search Console to measure your CLS on both field and lab data.
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Last updated: 2026-02-07