Image dimension sizing (width/height, aspect-ratio) and Cumulative Layout Shift
Explicit width and height attributes (72.0%), CSS aspect-ratio (3.5%), and unsized <img> tags (82.5%): how reserving image boxes moves Cumulative Layout Shift.
72.0% of sites use explicit width and height image dimension sizing, and 89% of those sites have a good CLS, against 88% of all sites.
CLS pass rate
Sites with explicit width and height image dimension sizing have a good CLS most often: 89%, against 88% of all sites. Sites with CSS aspect-ratio image dimensions have it least often, at 84%.
Image dimension sizing usage
Unsized <img> is the most used: 82.5% of sites. Explicit width and height is 72.0% of sites.
Understanding image dimension sizing
How browsers compute intrinsic aspect ratios from HTML width and height
User-agent stylesheets map HTML width and height attributes directly to an internal aspect-ratio property before the image file downloads. Across the web, 72.0% of sites size images with HTML width and height (89% good CLS), while 82.5% still include at least one unsized <img> (87% good CLS) and 3.5% use CSS aspect-ratio without HTML attributes (84% good CLS).
Set explicit width and height attributes on every <img> element so the browser reserves its aspect ratio before stylesheets or image bytes arrive. Across all audited sites, 72.0% include explicitly sized images (89% good CLS), whereas 82.5% still ship at least one unsized image (87% good CLS) and 3.5% rely solely on CSS aspect-ratio (84% good CLS).
How image dimension sizing plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,604 sites WordPress sets width and height on 92.2% of sites, while 74.4% also have unsized images.
WordPress core adds width and height attributes to media library images with wp_img_tag_add_width_and_height_attr(). Across WordPress, 92.2% of sites include explicitly sized images (89% good CLS) and 74.4% include at least one unsized <img> (88% good CLS).
Shopify 8,609 stores Shopify stores include width and height on 89% of storefronts (95% good CLS).
Shopify's Liquid image_tag filter outputs width and height attributes by default based on image dimensions. Across Shopify, 89.2% of stores have explicitly sized images (95% good CLS) and 73.6% also have unsized images (93% good CLS).
React & Next.js 9,590 sites React sites with HTML width/height (88.2%) pass CLS 9 points more often than sites with CSS-only aspect-ratio (5.0%).
Next.js <Image> requires width and height props unless fill is set. Across React sites, 88.2% include HTML width and height attributes (93% good CLS) and 5.0% use CSS aspect-ratio (84% good CLS).
By Arjen Karel · 212,308 crawled sites (197,524 with all devices Chrome field data, 195,226 sites with image dimension sizing, October 2026). How we measured.