Image Optimization for Website Speed and Core Web Vitals
How image size, dimensions, lazy loading, and WebP conversion affect performance and user experience.
Images are often the largest resources on a page. If a hero image loads slowly, users perceive the page as slow. If image dimensions are missing, the layout may shift while the page loads.
The image that becomes the Largest Contentful Paint element deserves special attention. Resize it to the displayed size, compress it carefully, and test a modern format such as WebP.
Lazy loading can help below-the-fold images, but the implementation should still be crawlable. Important image URLs should be present in rendered HTML rather than only appearing after a user action.
File compression is only the beginning. Dimensions, responsive image sources, caching, and page placement all affect the real performance users feel.
- Optimize above-the-fold images first.
- Resize images to the displayed dimensions.
- Compare WebP output against JPG or PNG.
- Set width and height to reduce layout shifts.
- Use crawlable lazy loading for lower-page images.