Compress Image to 20KB

Exam, job and government application portals often reject photos and signatures over 20 KB, and some also set a minimum, such as 10–20 KB. This tool finds the highest JPG (or WebP) quality that fits under your limit and only reduces the pixel size when quality alone is not enough. It works in your browser, so ID photos never leave your device.

How to use this tool

1. Choose the photo or signature (JPG, PNG, WebP and other browser-readable images).
2. Keep the maximum at 20 KB or type the limit your form states; add a minimum if the form has a range.
3. If the form asks for exact dimensions such as 200 × 230 px, enter them and choose crop, fit or stretch.
4. Download the result and check the final size and quality shown.

Formula

Binary search on quality q between 5% and 95%: encode, compare the size S(q) with the target T and halve the interval, about 8 encodes. If S(5%) > T, the pixel size is multiplied by 0.95 × √(T ÷ S) and the search repeats; it stops once 0.9 T ≤ S ≤ T.

File size grows roughly with the number of pixels, which is proportional to the square of the scale — hence the square root.

Example

A 3000 × 4000 px phone photo with a 20 KB maximum and an exact size of 200 × 230 px is centre-cropped to 200 × 230 px. That small picture usually fits at the top quality of 95%, so you get the clearest file the form allows; the result shows its exact byte count.