What it means
We flag images over 150 KB, and images whose files are much wider than the space they are shown in, for example a 3000-pixel photo displayed 400 pixels wide.
Why it matters
Every extra kilobyte takes time on a mobile connection and can delay the main content. Responsive images let phones download smaller files than desktops.
How to find it yourself
- PageSpeed Insights lists images that could be smaller under “Improve image delivery”.
- The Network panel in DevTools, filtered to images, shows each file’s size.
How to fix it
On any website
- Resize images to the largest size they’re displayed at, and offer smaller versions with srcset and sizes.
- Use WebP or AVIF, and compress JPEG and PNG files before uploading.
- Give images width and height attributes so they don’t shift the layout as they load.
On Shopify
- Shopify converts and resizes images on its CDN: use image_url with a width and image_tag with widths and sizes, instead of the original upload.
On WordPress and WooCommerce
- WordPress creates several sizes and adds srcset automatically; use an image optimization plugin or your CDN to serve WebP or AVIF.
How to check the fix
- Run the speed test again and compare the image list.
How FixReports finds it
The speed test lists images over 150 KB and images much wider than their displayed size, with each file’s weight and dimensions.