Image Optimization
Image optimisation means serving pictures at the right dimensions, in modern formats such as WebP or AVIF, compressed sensibly and lazy-loaded where that is appropriate. It is usually the largest single performance gain available on any content-heavy or ecommerce website.
Why it matters for your rankings
Images are the biggest thing on most pages by weight, often several times the size of all the code combined. That makes them the first place to look when a page is slow.
The typical failure is uploading a 4000 pixel wide photograph straight from a camera and letting CSS scale it down. The browser still downloads every byte. On mobile connections this is the difference between a page that loads in two seconds and one that loads in nine, and it directly determines Largest Contentful Paint. Optimisation also affects rankings through image search itself, where correct filenames, alt text and structured data can earn traffic that never appears in your standard keyword reports.
How to check it on your site
Find oversized images
PageSpeed Insights lists 'Properly size images' and 'Serve images in next-gen formats' with the exact savings available.
Convert to WebP or AVIF
These typically cut file size 25 to 50 percent against JPEG at equivalent quality, with universal modern browser support.
Set explicit dimensions
Width and height attributes prevent layout shift and improve your CLS score.
Lazy-load below the fold only
Never lazy-load your LCP image. Doing so delays the exact element Google is timing.