What is CLS?
CLS, or Cumulative Layout Shift, is a Core Web Vitals metric that scores how much visible content shifts unexpectedly while a page loads or is used. A lower score means a more visually stable page.
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Why CLS matters
Layout shifts are frustrating. You go to tap a button, an image loads above it, and the page jumps so you tap the wrong thing.
CLS is one of the three Core Web Vitals, which Google uses to assess page experience. Google's guidance treats a score of 0.1 or lower as good.
What causes layout shifts
Common causes include images and videos without set dimensions, ads or embeds that load late, and web fonts that swap in and change the text size. Content injected above existing content is another frequent culprit.
How to improve CLS
Set width and height on images and video, or reserve space for ads and embeds before they load. Avoid inserting new content above what people are already reading.
Use Google Search Console's Core Web Vitals report to find affected pages, then PageSpeed Insights or Chrome DevTools to find the elements causing the shifts.
Common questions
What does CLS stand for?
CLS stands for Cumulative Layout Shift. It reports the largest burst of unexpected layout-shift scores during a page visit, rather than the sum of all shifts over the visit.
What is a good CLS score?
A CLS of 0.1 or lower is good. Assess the 75th percentile of real page visits, separately for mobile and desktop.
Does CLS affect rankings?
Core Web Vitals are part of Google's page experience signals. They are one factor among many, and strong content relevance usually matters more.
How do I measure CLS?
PageSpeed Insights, Lighthouse, Chrome DevTools, and the Core Web Vitals report in Google Search Console can all show it. Field data from real users is the most representative.
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