Matan · SEO · Performance
CLS (lab)
Cumulative Layout Shift should stay under 0.1 so content does not jump while loading.
Pass condition in our engine: Lab CLS is under 0.1 when PageSpeed Insights is available.
1. Problem description
Ads, cookie banners, webfonts and images without dimensions push content down after first paint. It is a Core Web Vital and a conversion killer on mobile.
2. Most common causes
- Images and embeds without width/height.
- Banners injected at the top of the DOM.
- Font swap causing text reflow.
3. How to fix it
- Always set width and height (or aspect-ratio) on images and videos.
- Reserve space for ads and consent UI.
- Use font-display strategies that minimise shift.
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