Image optimization is one of those technical on-page tasks that's tedious to implement and invisible when done

Image optimization is one of those technical on-page tasks that's tedious to implement and invisible when done right — which is why so many sites skip it.

What's actually required:
- File format: WebP for most images (better compression than JPEG/PNG, supported by all modern browsers). AVIF for critical hero images on performance-sensitive pages.
- File size: no image should be larger than it needs to be for its display dimensions. A 3000px image displayed at 600px width is wasting load time.
- Alt text: descriptive, relevant to the image content, not keyword-stuffed. It's for accessibility first, SEO second.
- Lazy loading: images below the fold should use native lazy loading (loading="lazy" attribute). Reduces initial load time.
- Defined dimensions: width and height attributes prevent CLS from images that shift layout as they load.

Large images are almost always the biggest contributor to slow LCP scores. Fix images before investigating any other performance issue.