# CLS

> Cumulative Layout Shift — the Core Web Vital measuring how much the page jumps around while loading.

CLS quantifies the frustration of a page that moves under your finger: the button that slides away as you tap, the paragraph that drops mid-sentence when an ad loads above it. Each unexpected shift is scored by how much moved and how far, summed over the page's life; good is 0.1 or less, poor above 0.25. Deliberate moves — an accordion the user opened — do not count; only surprise shifts do.

The fixes are almost all reservations: width and height attributes on images and embeds so the slot exists before the content, font-display strategies and metric-matched fallbacks so text does not reflow when the real font lands, space held for ads and banners, and never injecting content above what the user is reading.

## Related terms

- https://dfieldsolutions.com/en/glossary/core-web-vitals.md
- https://dfieldsolutions.com/en/glossary/lcp.md
- https://dfieldsolutions.com/en/glossary/inp.md
- https://dfieldsolutions.com/en/glossary/lighthouse.md

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Source: https://dfieldsolutions.com/en/glossary/cls
DField Solutions — Dunakeszi, Hungary — dezso@dfieldsolutions.com
Booking: see https://dfieldsolutions.com/en/contact