Before you fight with an upload form, it pays to know your enemy. Forms rarely show the size of the file they rejected — they just fail, or worse, accept the upload and then crop or compress it themselves into something unrecognizable. This image size checker gives you the exact numbers first: total size in kilobytes and bytes, pixel dimensions, and the file format. Drop a file in and the answer appears instantly, with no upload, no processing, and nothing stored.
The checker is the natural first step in a compression workflow. Check the current size, compare it with the limit your form demands, and you immediately know how aggressive your compression needs to be. A 400 KB photo heading toward a 100 KB limit barely needs work; a 6 MB camera shot aimed at a 20 KB signature slot needs both quality reduction and a dimension cut. Measuring first turns guesswork into a plan.
It is equally useful after compressing. Download a resized image, drop it back into the checker, and confirm the kilobyte figure before you attempt the real upload — a five-second sanity check that saves another round of form rejection. Because the tool reads files locally through your browser's built-in file and image interfaces, it works the same offline as online, on desktop and mobile alike, with no size queue and no waiting.
Everything on this page respects the same privacy rule as our compressor: your images never leave your device. There is no server, no storage bucket, and no copy kept after you close the tab. Once you know your numbers, head to the compressor — the related links below include presets for the most common targets such as 20 KB and 100 KB — and bring the file under the limit in seconds.