Compress an image to 30 KB

Thirty kilobytes holds 240,000 bits. At roughly one bit per pixel that is a square of 490 pixels or a portrait of 420 by 570. A phone camera records about 12 million pixels, so the picture must shrink by a factor of fifty or more.

Forms that ask for a 30 KB photo often want a signature of 10 to 20 KB too. Do the photo here first, then change the target to Custom and type the smaller number for the signature. The two files never need to be joined.

At 30 KB, heavy compression can leave blocky patches on skin. If that happens, lower the dimensions slightly instead of quality. A smaller picture at higher quality looks cleaner than a larger one that is crushed.

The tool finds a good result in one pass, but only you can say whether it is good enough for your purpose. A passport-style photo and a product picture judge sharpness differently. Look at the result at the size it will actually be shown, not blown up to fill your screen.

If the picture looks fine there, you are done. If not, change one thing at a time: crop tighter, then change the size, then the format.

Eyes and mouth carry most of the meaning in a portrait. If you have to choose where to lose detail, lose it in hair and background. Crop so the face fills the frame, and the compressor will save its bytes on the edges instead.

Avoid hats with brims that cast shadows across the eyes, because dark flat shadow patches turn blocky when the file is this small.

Before you upload the picture, open it on your phone and on your computer. The two screens differ in sharpness and brightness, so a picture that looks fine on one may be judged differently on the other. If you are happy with both, the result is safe.

Hats with a brim deserve the same care as the earlier tip, since the dark band across the eyes is the first thing to go blocky.