ImageDimensions

Find the oversized images slowing down any website

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Point the scanner at any URL and it lists every image on the page next to two numbers: the file's real dimensions and the size it's actually displayed at. That gap is where the waste hides, like a 3000px hero image rendered at 400px. It runs a full headless-Chrome render of the page, so it catches images that only load after JavaScript, not just what's in the raw HTML. There are also two converters, PNG to WebP and JPG to WebP. Those run entirely in your browser. Nothing gets uploaded; the conversion happens locally with WebAssembly, and you can watch your Network tab stay quiet while it works. Free, no signup, no watermarks.

ImageDimensions scans any webpage and reports each image’s natural and rendered dimensions to spot oversized assets.

for: Web developers and performance engineers who optimize site images.
pricing: free

Key features

6 features of ImageDimensions

Full page scan — Enter a URL and the tool renders the page with headless Chrome, capturing all images including those loaded via JavaScript.
Natural vs rendered size — Shows each image’s original pixel dimensions and the size it actually occupies on the page.
Background image detection — Analyzes CSS background images as well as inline <img> tags.
Browser-based converters — Convert PNG/JPG to WebP locally with WebAssembly; files never leave the browser.
No signup or watermarks — All scanning and conversion features are free and require no account.
Privacy-respecting crawl — Honors robots.txt and respects CORS restrictions during scans.

Use cases

Audit a production site for image bloat that hurts Core Web Vitals
Identify and replace oversized hero images to improve load speed
Convert legacy PNG/JPG assets to WebP directly in the browser
Check a single image’s dimensions before adding it to a page
Generate a report of all images on a page for a performance review

ImageDimensions FAQ

How do I check image dimensions on a website?+

Paste the page URL into the scanner; it loads the page in a real browser, renders JavaScript, and reports every image with its natural and rendered sizes.

Do I need to install anything?+

No. The scanner runs on the server and returns results in your browser; converters run locally with WebAssembly.

Is the tool free?+

Yes—both the scanner and all browser-based tools are free with no signup or watermarks.

Can it scan any site?+

It works on any publicly reachable page, but cannot scan pages behind logins, private networks, or sites that block automated visitors.

What about cross-origin images?+

If a host blocks CORS, file size may be unavailable, though dimensions are still reported.

Summarized by DevHunt from imagedimensions.com · Sep 28, 2026. Details may change; check the official site.