What fits in 20 KB
Twenty kilobytes is about the size of ten pages of plain text. A photo from a phone is a hundred times bigger or more. To fit, the picture has to lose detail in two ways: stronger compression, and fewer pixels. A face photo that is a few hundred pixels across and compressed well still shows features clearly, which is enough for most identity forms. A signature on a white background compresses extremely well because there is so little in it.
The tool works in a fixed order. It first tries the level you chose, and uses it if it fits. Then it tries qualities from high to low and keeps the best one that fits. If the whole picture fits at the lowest acceptable quality it keeps every pixel. Only if even that is too big does it shrink the picture in steps and try again at a better quality. That order matters: lowering the quality a little is nearly free in looks, while losing pixels is not.
Getting a better result at 20 KB
- Crop first. With the Crop Image tool, cut away everything that is not needed. Plain backgrounds compress well, but cropping removes the bits altogether.
- Start from a sharp picture. Blur and noise are expensive: a clean photo compresses to a better result than a grainy one.
- Check the form's size rules. Some forms also set pixel dimensions or a ratio. Set the longest side in this tool, or use Resize Image first.
- Do not compress twice. Start from the original, not from a version that was already compressed.
Preparing a passport style photo for a 20 KB limit
Forms that ask for a tiny photo usually care about three things: the file type (almost always JPG), the pixel size or proportions, and the maximum size in kilobytes. Doing the steps in the right order gives the best picture for the space.
- Start from the original. Use the sharpest, evenly lit photo you have, not one that was already shrunk or passed through a messaging app. Compressing a compressed picture adds loss on top of loss.
- Crop first. With Crop Image, choose the shape the form wants so the face fills the frame. Every pixel of empty wall costs bytes.
- Set the pixel size if the form gives one. Resize Image can set exact dimensions. Do this before compressing: this tool only ever makes a picture smaller, so resizing afterwards would re-encode it and could push it over the limit.
- Choose JPG. If your picture is a PNG or a HEIC photo and the form wants JPG, pick JPG under Format. A photo is many times smaller as JPG than as PNG.
- Compress to 20 KB, then compare. Open the compare view and look at the eyes and the outline of the face at 100 percent.
Signatures and handwriting at 20 KB
A signature is the easy case. Dark ink on plain paper has almost no detail to keep, so it compresses extremely well. In our test, a scan of a signature 1,200 pixels wide that started at 96 KB came out at about 8.6 KB at the Balanced level, so a 20 KB limit was met without making the scan any smaller in pixels.
To get a clean result, sign with a dark pen on white paper, scan or photograph it in even light without shadows, crop away the margin, and compress. A grey or coloured background is what uses up the space, not the ink.
When a form also has a minimum size
Some forms set a range, such as between 10 and 20 KB. This tool stays at or under the limit, and a very simple picture can come out well below it because there is nothing more to store. A file cannot be made bigger in kilobytes without adding pixels, so if a form rejects a file for being too small, start again from a larger original, or use a larger limit and check what the form accepts.