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What's the impact of lazy loading images on CLS scores?
Asked on Mar 06, 2026
Answer
Lazy loading images can significantly improve your CLS (Cumulative Layout Shift) scores by preventing unexpected content shifts during page load. This technique ensures that images are only loaded when they are about to enter the viewport, reducing the initial load time and stabilizing the layout.
Example Concept: Lazy loading images helps maintain a stable layout by reserving space for images before they are loaded. By using the "loading='lazy'" attribute on image tags, browsers can defer loading images until they are needed, which minimizes layout shifts and improves CLS scores.
Additional Comment:
- Lazy loading is particularly effective for images below the fold, as it reduces the number of requests during the initial page load.
- Ensure that images have defined width and height attributes to prevent layout shifts when they load.
- Modern browsers support native lazy loading, making it easy to implement with minimal code changes.
- Test your site with tools like Lighthouse to measure the impact of lazy loading on CLS and other Core Web Vitals.
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