20 KB
Resize a photo to exactly 20 KB
20 KB is 20,480 bytes. This page is preset to that number, and the tool lands on it exactly whether your file needs to shrink or grow. Everything runs in your browser, so your photo is never uploaded. 20 KB is most often asked for on signature uploads on most application portals.
Updated , written and tested by Rizwan Aslam
Resize your photo to 20 KB
Preset to 20 KB. Change the number if your form asks for something else.
What 20 KB actually looks like
Twenty kilobytes is the standard signature slot on Indian application portals, which is why it shows up more often than almost any other number. The catch is that scanned signatures often arrive far heavier than 20 KB, because paper grain and shadow give the compressor thousands of tiny details to store. Scanning on a flat white surface with good light does more for this target than any tool setting.
This is a small target. Almost every photo arriving here has to shrink, often by a very large factor, so the pixel dimensions matter more than they do anywhere else. The measure that decides this is bits per pixel: the file size in bits divided by the number of pixels. Here is what 20 KB gives you at three sizes.
| Dimensions | Pixels | Bits per pixel | Result |
|---|---|---|---|
| 300 x 400 | 0.12 MP | 1.37 | Excellent, no visible difference |
| 600 x 800 | 0.48 MP | 0.34 | Heavy artifacts, clearly degraded |
| 1200 x 1600 | 1.92 MP | 0.09 | Heavy artifacts, clearly degraded |
The largest photo that still looks very good at 20 KB is around 390 by 520 pixels. That is the point where this target still delivers roughly 0.8 bits per pixel. Above it, quality starts dropping whatever tool you use.
Both directions, one page
At a target this small the shrink case is almost the only one that happens, but the grow case still matters for signature scans that came out unusually light. Most sites give you one tool to grow a file and a different one to shrink it, but the same algorithm does both, so this page does both.
| Your file | What the tool does | Picture quality |
|---|---|---|
| Over 20 KB | Binary searches encoder quality downward until it fits, then pads back up to the exact byte | As good as 20 KB allows |
| Under 20 KB | Raises encoder quality as high as still fits, then pads the remainder losslessly | Slightly sharper than before |
| Already 20 KB | Nothing at all, and it tells you so | Untouched |
The padding is not a trick. Every major format reserves a block for data decoders skip, so writing neutral bytes there changes the file size and not one pixel.
Getting 20 KB accepted
Three things worth knowing before you upload.
- Shrink the dimensions first. At this size the pixel count is what decides whether the result is readable.
- Keep signatures on white. A clean white background compresses to almost nothing, so all the bytes go to the ink.
- Check for a minimum. Small targets are usually written as a range, and compressing as hard as possible drops you under the floor.
More rejection messages and what each one really means are in the guide to why forms reject photos.
Questions about the 20 KB target
Can a photo really work at 20 KB?
Only at small pixel dimensions. At 300 by 400 the result is 1.37 bits per pixel, which reads as excellent, no visible difference. At 1200 by 1600 the same 20 KB gives 0.09 bits per pixel and the picture falls apart. Resize first.
The form says my file is too small. What now?
That means there is a minimum as well as a maximum. Compressing as hard as possible pushed you under it. Pick a number inside the range rather than the smallest possible file and run it again.
Is 20 KB enough for a signature?
Usually yes, and more comfortably than for a photo. A signature is ink on white, so most of the image compresses to almost nothing and the bytes go where the detail actually is.
Should I use JPG or PNG at this size?
JPG, unless the form insists otherwise. PNG stores everything losslessly, so a PNG at 20 KB means shrinking the picture drastically to fit. JPG gets you far more picture for the same bytes.