Compress Image to 30 KB

Thirty kilobytes is a frequent limit on government, exam and recruitment portals, often as a range — a photo of 10–30 KB or a signature of 10–20 KB. Too large is rejected, and on some forms so is too small. This tool hits both ends: it finds the highest quality that stays under the maximum and, when a JPG ends up below the minimum, pads it with harmless comment bytes to exactly the minimum. It works in your browser, so ID photos never leave your device.

How to use this tool

1. Add the photo or signature scan.
2. Enter the maximum (30 KB) and the minimum from the form, for example 10 KB.
3. If the form asks for exact pixels, such as 200 × 230 px, enter the width and height; tick greyscale for signatures.
4. Download the JPG and check that the byte count shown falls inside the range.

Formula

size(q, w × h) ≤ maximum, solved by binary search on q between 50% and 92%; if even 50% is too big, both sides shrink by about 0.95 × √(limit ÷ size). If the result is under the minimum, the top quality is tried and the JPG is then padded with COM (comment) segments to exactly the minimum.

Comment segments are part of the JPEG standard and are skipped by every decoder, so the picture is unchanged. In "Safe for both" mode the maximum counts 1 KB as 1,000 bytes and the minimum as 1,024 bytes, which satisfies either kind of check.

Example

For a range of 10–30 KB in safe mode, the file must be 10,240–30,000 bytes. A 200 × 230 px passport-style photo usually fits under 30,000 bytes at a high quality; a 140 × 60 px signature might be only 3,000 bytes, so it is padded to exactly 10,240 bytes.