ImageDimensions — Image Size Auditor von Full Cycle Development Group

Every image on a page has two sizes: the pixels in the file, and the pixels the browser actually draws. When the first is much larger than the second, the visitor downloads weight they never see — and it is invisible until you go looking.

ImageDimensions shows you both numbers for every image on the page you are on, sorted worst first.

WHAT YOU GET

• Every image measured — the file's real pixel size next to the size it was drawn at
• A multiplier showing how much was wasted, so a 3000×2000 file in a 250×167 slot reads plainly as 144×
• CSS background images included — roughly a fifth of the images on a typical page, and most audits skip them entirely
• Click any row to scroll straight to that image and highlight it on the page

WHY NOT JUST USE A WEBSITE SCANNER

Hosted scanners load your page in a headless browser somewhere else. That means they cannot see anything behind a login, anything protected by a bot filter, or anything running on localhost or a staging domain — which is exactly where you are working when the problem is still cheap to fix.

This runs in your browser, on the page in front of you.

IT MEASURES AGAINST YOUR ACTUAL DISPLAY

A 400×400 image in a 200×200 slot is wasteful on a standard display and exactly right on a retina one. A headless scanner cannot tell the difference, because it does not have a screen. This extension knows your real device pixel ratio, so it will not flag a correctly-served retina image — and it will flag one that is oversized even after retina is accounted for.

PRIVACY

No account. No network requests. No analytics. No storage. Nothing about the pages you visit leaves your machine, because nothing is ever sent anywhere.

It asks for two permissions and no more: permission to read the current tab when you click the icon, and permission to run the measurement on that click. There are no host permissions, so it has no standing access to any site.

The source is public: github.com/Bishop81/imagedimensions-extension

FROM THE MAKERS OF IMAGEDIMENSIONS.COM

The same measurement is available as a hosted scanner, an MCP server for AI coding agents, and a CLI with a GitHub Action for failing a build on oversized images. See imagedimensions.com