2026-03-12

What an exact KB image compressor actually does

Most image tools ask for a quality percentage. Upload forms ask for a file size. Those are not the same control. A quality of 80 on a 4000 pixel photo can be several megabytes. The same quality on a soft 800 pixel photo can be 40 KB.

An exact KB compressor flips the problem. You name the budget. The software searches for an encode that fits.

The two knobs that matter

Quality. JPEG and WebP can spend fewer bytes on a lower quality setting. KBPass binary-searches that setting and keeps the largest one that still measures under the target.

Dimensions. If even the lowest quality is over the budget, pixels have to go. The tool scales width and height together so the picture is not stretched, then searches quality again. The compare slider and the dimension line show what changed.

PNG is the exception. Its encoder does not accept a quality value, so Auto mode converts PNG to WebP and says so. Details are in the PNG guide.

What “exact” does not mean

The output is at or under the target, not a promise of hitting 49,999 bytes every time. The winning encode is the best measured candidate under the cap. If the image cannot be reduced far enough, the badge says the target was missed and you still get the smallest file the search produced.

Why it stays on your device

There is no upload step, because the search only needs the pixels and an encoder. Both exist in the browser. A worker does the encodes so the page can keep drawing. That is the whole product: open the tool, set KB or MB, download the file.