Matan · Performance · Core Web Vitals
Image width and height (Performance)
Missing dimensions are the most common cause of Cumulative Layout Shift.
Pass condition in our engine: At least 80% of homepage images declare width and height.
This Performance check is part of SEO-GEO scoring 2.2.1, last updated 2026-09-18. About 90 percent of the evaluation runs on the HTML we crawl, so you can verify the same pass condition with a free report.
1. Problem description
The browser cannot reserve space until the image bytes arrive, so text jumps when the file loads. CLS above 0.1 fails Core Web Vitals.
2. Most common causes
- CMS templates omit width/height.
- Responsive images with only max-width in CSS.
- Late-injected ads and embeds.
3. How to fix it
- Set width and height attributes (or CSS aspect-ratio) on every img and video.
- Reserve space for ads and cookie banners.
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