CLS
Cumulative Layout Shift
In one line
CLS (Cumulative Layout Shift) is the Core Web Vitals metric for visual stability — it sums up how much page elements jump around unexpectedly while the page is loading.
Going deeper
CLS (Cumulative Layout Shift) sums up how much elements move around unexpectedly during page load. It is the visual-stability member of the Core Web Vitals trio (LCP, CLS, INP). Anything at or below 0.1 is considered good; 0.25 and above needs work.
The usual culprits are predictable: images or iframes without explicit dimensions, ads or banners injected dynamically, and late-loading web fonts that reflow text. Setting width and height and reserving ad slots in advance fixes most of the score on its own.
CLS still matters in the GEO era. Pages that feel unstable get penalised in search, and pages that fall in search drift out of AI citation pools too. Page experience signals tend to act on AI inclusion indirectly but reliably.
Sources
Related terms
INP
INP (Interaction to Next Paint) is the Core Web Vitals metric that captures overall interaction responsiveness across a session — and it officially replaced FID in March 2024.
SEOFCP
FCP (First Contentful Paint) measures the moment any meaningful content — text or image — first appears on screen, used as a supporting page-speed metric alongside Core Web Vitals.
SEOTTFB
TTFB (Time to First Byte) measures how long it takes from a request being sent until the first byte of the response arrives — a foundational metric for server responsiveness and LCP work.
SEOMobile SEO
Mobile SEO covers the rendering, speed and UX of your site on mobile devices — effectively a baseline expectation since Google moved to mobile-first indexing.
SEOTechnical SEO
Technical SEO is the infrastructure-level work — crawling, indexing, rendering, speed, structured data — that makes a site readable and rankable for search engines in the first place.
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