How to compress image to 20 KB
- Tap Choose a photo and pick the image the form rejected.
- The target is already 20 KB. Tap Compress to 20 KB.
- Read the size on the result — it will say whether 20 KB was reached.
- Save the file if you are happy with how it looks.
What actually fits in 20 KB
A signature on white paper fits easily — there is almost nothing in the picture to store. A head-and-shoulders photograph against a plain wall fits comfortably at a few hundred pixels across. A group photograph, a busy street, or a scan of a page of printed text will not fit at any quality worth handing in, because detail is the thing that costs bytes and those pictures are made of it.
When the page cannot reach 20 KB it does not refuse and it does not quietly give you something unusable. It hands over the smallest readable version it produced, prints the real size, and stops shrinking before the picture stops being a picture.
Crop before you compress
The single most effective thing you can do for a 20 KB target is to remove the parts of the frame nobody needs. Half the pixels is roughly half the bytes at the same quality, and cropping tightly around a face costs you nothing the form wanted in the first place.
Photographing a signature against a plain white sheet in even light is the other half of the trick. Shadows and paper texture are detail, and detail is what fills up twenty kilobytes.