Compress Image to Size

By trying. It encodes the image at a high quality, measures the result, and halves its way towards the target — a binary search, usually seven or eight attempts per picture. There is no formula that maps quality to file size, because the answer depends on the picture: fine detail and noise cost far more bytes than flat colour, so the same setting produces wildly different sizes for different photos.

Type the target and it searches for the quality that lands just under it — compress jpeg to 50kb, or any other figure, without the guess-and-check of a quality slider. It is the same search whatever the number, which is why compress image to exact size is the honest description: the tool works backwards from the limit you were given.

Yes. Drop in a folder and every picture is squeezed under the same limit independently, because a target of 100 KB means each file under 100 KB rather than the set of them. Each one gets its own quality search, so a simple graphic keeps more quality than a detailed photograph while both land under the number.

Drop it in, type 100 KB as the target, and the tool searches for the highest quality that still fits under it. That search is the difference between this and a quality slider: a slider makes you guess and check, while this does the guessing — usually eight to twelve attempts, all of them in your browser, none of them uploaded. The same works for any figure, so compress a JPEG to 50KB or an image to 1MB by typing that instead.

This tool treats 1 KB as 1,024 bytes, which is what upload limits almost always mean and what Windows shows you. So a 100 KB target means 102,400 bytes. If a form is rejecting a file that this tool says fits, that difference is the first thing to check.

Yes — drop in up to thirty and they all get squeezed under the same limit. Each one is searched separately, which is the reason to do them together rather than one at a time: the same 200 KB cap might land at 90% quality for a simple graphic and 60% for a detailed photograph, so a single shared setting would be wrong for most of a folder. They download as a zip, and one image on its own still downloads as an ordinary file.

Because there is a floor. Below roughly 20% quality an image becomes visibly blocky, and a large photo simply cannot fit into a very small file at any setting — twelve megapixels will not become 20 KB and still be a photograph. When that happens the tool says so for that file rather than handing back a smear, and suggests reducing the dimensions, which is the lever that actually works at that point. In a batch the others still finish.

It picks whichever of JPEG or WebP suits the image, since PNG has no quality dial to search over — it is lossless, so the only ways to shrink it are fewer colours or fewer pixels. If you need the result to stay PNG, resize it instead.

No. The compression runs in your browser using the same graphics code that draws the page, so the file never leaves your machine. There is a public API for scripts, which does run on our servers, but the tool on this page does not use it.

The image compressor takes a quality and tells you the size. This takes a size and finds the quality. If you just want a smaller file, that one is simpler and lets you see the trade-off. If something has given you a number you must fit under, this one is the tool that answers it.