WordPress image dimensions and Cumulative Layout Shift
Explicit width and height attributes (92.2%), CSS aspect-ratio (2.5%), and unsized <img> tags (74.4%): how reserving image boxes moves Cumulative Layout Shift.
92.2% of WordPress sites use explicit width and height image dimension sizing, and 90% of those sites have a good CLS, against 90% of all WordPress sites.
CLS pass rate
Sites with explicit width and height image dimension sizing have a good CLS most often: 90%, against 90% of all WordPress sites. Sites with unsized <img> image dimensions have it least often, at 90%.
Image dimension sizing usage
Explicit width and height is the most used: 92.2% of WordPress sites.
Image dimension sizing per framework
React sets the image dimension sizing to explicit width and height on 95% of its sites, and 88% of React sites have a good CLS, against 90% of all sites. Alpine sets the image dimension sizing to unsized <img> on 88% of its sites, and 89% of Alpine sites have a good CLS.
jQuery 60,046 sitesExplicit width & height attributes 93%Unsized <img> (no width/height or aspect-ratio) 75%90%
Vue 4,829 sitesExplicit width & height attributes 95%Unsized <img> (no width/height or aspect-ratio) 86%90%
Alpine 379 sitesUnsized <img> (no width/height or aspect-ratio) 88%Explicit width & height attributes 78%CSS aspect-ratio only 12%89%
React 2,226 sitesExplicit width & height attributes 95%Unsized <img> (no width/height or aspect-ratio) 81%88%Image dimension sizing or the framework
Does the framework explain the image dimension sizing difference?
Almost every site with explicit width and height image dimension sizing is a jQuery site, and almost every jQuery site has explicit width and height image dimension sizing, so the data can't tell explicit width and height image dimension sizing and jQuery apart. On Vue, 90% 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. On React, 87% of sites with explicit width and height image dimension sizing have a good CLS, against 88% of React sites with unsized <img>. Within React, 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, 92.2% of sites size images with HTML width and height (90% good CLS), while 74.4% still include at least one unsized <img> (90% good CLS) and 2.5% 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, 92.2% include explicitly sized images (90% good CLS), whereas 74.4% still ship at least one unsized image (90% good CLS) and 2.5% rely solely on CSS aspect-ratio (90% good CLS).
By Arjen Karel · 63,295 crawled WordPress sites (36,524 with phone Chrome field data, 62,969 sites with image dimension sizing, October 2026). How we measured.