AI SEO Glossary
What is CLS?
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TL;DR — Cumulative Layout Shift (CLS) measures how much a page's visible content unexpectedly moves during the visit, scored by how large the shifting elements are and how far they travel. Google's "good" threshold is 0.1 or less at the 75th percentile of real visits. CLS quantifies the experience everyone recognizes: you go to tap a button and a late-loading banner shoves it down the page. On a store, layout shift isn't cosmetic — it causes mis-taps on the exact elements (add to cart, checkout, cookie consent) where errors cost money.
Definition & scope
The main causes are images and embeds without reserved dimensions, injected banners and app widgets, and web fonts swapping at different metrics. Shifts triggered within 500ms of a user interaction don't count — the metric targets unexpected movement.
Prevention is architectural: reserve space for everything that loads late, size media explicitly, and make third-party widgets render into fixed slots instead of pushing content.
Related terms
- Core Web Vitals — CLS is one of the three.
- LCP — the loading counterpart.
- INP — the responsiveness counterpart.
Related services
- Custom Website Design — layouts designed with reserved space for dynamic content.
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