Free Image Size Checker

How heavy is too heavy?

As a rule of thumb, most images on a page should be under 200 KB, and the whole page well under 1 to 2 MB of images. The checker sorts every image into these bands, heaviest first, so you know where to start:

We tested one phone screenshot

To show what's at stake, we took one ordinary phone screenshot, 1290 × 2796 pixels, saved as a PNG at 2,599 KB, and re-saved it at the same size in each format:

Same picture, same dimensions: from 2.6 MB to 74 KB. Every visitor on a phone downloads whichever version you upload, so the format and compression you choose matter more than almost anything else on the page. Photos usually see smaller, but still large, savings than screenshots.

Which format for which image

A five-step routine before every upload

This is the fix that doesn't need a developer. Do it before an image goes on your site:

1. Resize to the size you'll show it. If a photo is displayed 800 pixels wide, export it at about 1600 for sharp phone screens, not 4000.
2. Choose the format. WebP for photos and most graphics, SVG for logos and icons.
3. Compress at quality 75–85 and compare it with the original at full size.
4. Name it and describe it. A clear file name and alt text help image search and screen readers. The Meta Tag Checker counts images missing alt text.
5. Check the page. Run it through this checker, then test it on a phone with the Mobile-Friendly Checker.

What each flag means

Oversized or heavy

The file is over 500 KB or between 200 and 500 KB. Compress it, and resize it if it's much bigger than its display size.

Could be WebP or AVIF

A JPEG or PNG over 100 KB. The estimate assumes about a 30% saving, a conservative figure; screenshots often shrink far more, as the test above shows.

Served at X px, shown at Y px

The file is more than twice as wide as the space it fills. Only reported when the page states the display width and the image doesn't already use srcset.

First image is lazy-loaded

The first image on the page has loading="lazy". If it's your main banner, that delays it. Lazy-load images further down instead.

Lazy loading: when it helps and when it hurts

Lazy loading tells the browser to wait until an image is about to scroll into view before downloading it. That's ideal for long pages and galleries, because visitors who never scroll never download those files. It hurts when it's applied to the main image at the top: the browser holds off on the very image people see first, which slows down Largest Contentful Paint. Give every image a width and height too, so the layout doesn't jump as images arrive.

What this checker can't see

• Images added by JavaScript or set in CSS files aren't in the page's HTML, so they don't appear here.
• It checks one page. Heavy images often repeat across a site, for example in a header or a product template. Watch Owl checks every page.
• Sizes are what we download. Some image services send different files to different devices, so a phone may get a smaller version than we measured.

Light images on one map

Broken or missing images are a separate problem: the Broken Link Checker finds them. If your share image is too heavy for social platforms, the Open Graph Checker will flag it.