Shopify image dimensions and Cumulative Layout Shift
Explicit width and height attributes (89.1%), CSS aspect-ratio (4.0%), and unsized <img> tags (73.9%): how reserving image boxes moves Cumulative Layout Shift.
89.1% of Shopify sites use explicit width and height image dimension sizing, and 95% of those sites have a good CLS, against 94% of all Shopify sites.
CLS pass rate
Sites with explicit width and height image dimension sizing have a good CLS most often: 95%, against 94% of all Shopify sites. Sites with CSS aspect-ratio image dimensions have it least often, at 90%.
Image dimension sizing usage
Explicit width and height is the most used: 89.1% of Shopify sites.
Image dimension sizing per framework
Vue sets the image dimension sizing to explicit width and height on 93% of its sites, and 90% of Vue sites have a good CLS, against 94% of all sites. jQuery sets the image dimension sizing to unsized <img> on 89% of its sites, and 91% of jQuery sites have a good CLS.
jQuery 3,144 sitesUnsized <img> (no width/height or aspect-ratio) 89%Explicit width & height attributes 76%91%
Vue 933 sitesExplicit width & height attributes 93%Unsized <img> (no width/height or aspect-ratio) 83%90%Image dimension sizing or the framework
Does the framework explain the image dimension sizing difference?
On jQuery, 91% of sites with explicit width and height image dimension sizing have a good CLS, against 90% of jQuery sites with unsized <img>. Within jQuery, sites with explicit width and height and unsized <img> have a good CLS about equally often. On Vue, 91% of sites with explicit width and height image dimension sizing have a good CLS, against 89% of Vue sites with unsized <img>. Within Vue, sites with explicit width and height and unsized <img> have a good CLS about equally often.
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, 89.1% of sites size images with HTML width and height (95% good CLS), while 73.9% still include at least one unsized <img> (93% good CLS) and 4.0% use CSS aspect-ratio without HTML attributes (90% good CLS).
Understanding image dimension sizing
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, 89.1% include explicitly sized images (95% good CLS), whereas 73.9% still ship at least one unsized image (93% good CLS) and 4.0% rely solely on CSS aspect-ratio (90% good CLS).
By Arjen Karel · 8,246 crawled Shopify sites (5,825 with phone Chrome field data, 8,223 sites with image dimension sizing, October 2026). How we measured.