Performance Tools

Image Optimization Checker

Check a page's images for the problems that slow loading and make layouts jump.

Checks up to 8 images found on the page.

Not sure what to enter? Try an example: wordpress.org

Free & instant No signup How to use FAQ

Enter a URL to check every image on the page for missing dimensions, missing lazy loading and files that are too large.

How do I optimize images on a web page?

Images are usually the heaviest part of a page. This checker looks at a page's images for missing width/height (which causes layout shift), missing lazy loading on images further down the page, and oversized files that could be compressed or served in a modern format such as WebP or AVIF.

How to check a page's images

Enter the domain or URL in the box above.
Click Check Images.
Review images flagged for missing dimensions, lazy loading or large size.
Add width and height, use loading="lazy" below the fold, and compress or convert large images.

Related checks

Images also need alt text - check it with the Image Alt Text Checker.
To check the HTML size, use the Page Size Checker.

Convert large JPEG and PNG files to WebP or AVIF, size them to the width they are actually shown at, and lazy-load images below the fold. JustChecker tracks page weight and speed over time.

Frequently Asked Questions

They let the browser reserve space before the image arrives, so text doesn't jump around while the page loads - Google measures this as Cumulative Layout Shift.

Every image below the fold, yes (loading="lazy"). Don't lazy-load the main image at the top of the page, or it will appear later.

Resize them to the size they are shown at and convert them to WebP. The Image Resizer and Image Compressor do both in your browser.

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