About the Image Optimization Checker
Images are often the largest part of a page's weight. This image optimization checker runs Lighthouse through PageSpeed Insights on a public URL and lists images that are larger than their displayed size, not efficiently compressed, not in modern formats like WebP or AVIF, or offscreen and loaded before they are needed, with estimated savings for each.
Fixing these issues reduces data use and can speed up Largest Contentful Paint when the main image is affected. Resize images to the dimensions they are shown at, serve several sizes with srcset, compress them, convert to WebP or AVIF and lazy-load images below the fold. Our image compressor, converter and resizer can handle these steps in your browser.
How to use it
- Enter a public page URL.
- Review the list of flagged images and estimated savings.
- Resize, compress or convert the largest offenders.
- Replace the images on your site and re-test the page.
Frequently asked questions
What does properly size images mean?
It means the image file's dimensions should be close to the size it is displayed at. A 3000-pixel-wide photo shown in a 600-pixel column wastes bytes. Use srcset and sizes so the browser can pick a suitable version for each screen.
Will converting to WebP or AVIF reduce quality?
At sensible quality settings, most people do not notice a difference, and file sizes are often much smaller than JPG or PNG. Check important images, such as product photos, at full size after converting, and adjust the quality if needed.
Should the main image be lazy-loaded?
No. The largest image visible on load, often the LCP element, should load immediately and can use fetchpriority="high". Lazy-loading it delays LCP. Lazy-load images further down the page instead. Our lazy loading checker can confirm which images on a page are lazy-loaded and whether the first images are loading too late.