How to Compress an Image to 20KB (Signatures and Small Photos)
To compress an image to 20KB without it looking blocky, crop and resize the pixel dimensions down first, then compress to the target. Signatures compress easily to 20KB since most of the image is plain white; small photos need both a tight crop and moderate compression to look clean at the same size.
To compress an image to 20KB, first crop and resize it down to a small pixel size, roughly the size of a signature or a small passport photo, then compress with a JPG quality setting low enough to hit the target. Trying to compress a large, uncropped photo straight to 20KB almost always produces a blurry, blocky mess, since there simply is not enough room to store that much detail at that file size.
Why 20KB needs a different approach than 100KB or 200KB
At larger targets like 200KB or 500KB, a compressor can often shrink a normal-sized photo without you noticing much quality loss, because there is still plenty of file size budget to work with. At 20KB, that budget is tiny, about as much as a few pages of plain text, so the only way to get a genuinely sharp result is to reduce the pixel dimensions first and let the file naturally need less data. This is exactly why signatures, which are simple line art rather than detailed photographs, are the most common thing asked for at 10-20KB, while a full face photo at 20KB usually needs to be quite small in pixel terms too.
| Source | Typical pixel size for a clean 20KB result | Notes |
|---|---|---|
| Signature (line art on white) | A small, wide crop, such as the about 6.0cm x 2.0cm that SSC asks for | Compresses very efficiently since most of the image is plain white |
| Small ID-style photo | Small, tightly cropped face photo | Needs both a small pixel size and moderate compression together |
| Full-size uncropped photo | Not realistic at 20KB without heavy quality loss | Crop and resize first rather than compressing the full frame |
Hit the target directly with the Compress Image to 20KB tool, or use the Resize Signature to 20KB preset if you are specifically working on a signature.
Compress an image to 20 KB here
Add a JPG, PNG or phone photo. It saves the best quality that stays at or under 20 KB.
Runs in your browser. Your file never leaves your device. Open the full Compress Image to 20 KB page
Step by step
- Crop the image tightly to just the subject: the face for a photo, or just the ink for a signature, with only a small margin.
- Resize the cropped image down to the pixel dimensions your form specifies, or a similarly small size if no exact pixel figure is given.
- Run the resized image through the compressor with a target of 20KB.
- Zoom in on the result at 100% to check for blockiness or smudging before you rely on it.
- If it still looks rough, crop even tighter, since a smaller starting image compresses more gracefully at the same 20KB target.
Signatures specifically
A signature is one of the easiest things to compress to 20KB cleanly, precisely because most of the image is plain white background with only a thin dark line of ink. Sign with a dark pen on plain white paper, photograph it with even light and no shadow, crop tightly around just the signature, and it should compress to well under 20KB with room to spare, often letting you use a slightly larger crop for a clearer final look.
If your signature file keeps landing well below 10KB even at a reasonable crop, the pen might be too light or the scan too small. Re-sign with darker ink or scan slightly larger, then crop and compress again, rather than trying to artificially inflate a thin, faint scan.
Small photos specifically
A small ID-style photo is harder to compress this small than a signature, since a real face has far more fine detail, like hair, skin tone variation and shadows, that the compression has to approximate. Expect visibly softer detail at 20KB than you would see at 50KB or 100KB, and treat this as a normal trade-off for a very small file size limit rather than a sign that something went wrong.
Common mistakes
- Skipping the resize step and trying to compress a full-resolution photo straight to 20KB, which produces heavy blockiness.
- Saving as PNG instead of JPG, since PNG rarely compresses a photograph this small without looking worse than JPG at the same size.
- Not checking the final crop and pixel size against what the specific form actually asks for, and ending up with a technically 20KB file in the wrong dimensions.
- Compressing the same file repeatedly instead of starting fresh from a well-cropped source each time.
- Photographing a signature or photo at an angle instead of straight on, which forces an awkward crop later and wastes pixels on background that could have gone toward detail.
Converting from other formats first
The Compress Image to 20KB tool accepts JPG, PNG, WebP and HEIC files, so an iPhone photo can go straight in. If you are doing all of this on a phone and want the Android and iPhone steps, including how to set an iPhone to shoot JPG, see our guide on reducing photo size in KB on mobile. Always check that the final file matches the format the form asks for, which is usually JPG.
A note on signatures specifically for exam forms
Many Indian exam forms specify both a KB range and a rough physical dimension for a signature, such as roughly 6.0cm wide by 2.0cm tall. When you are aiming for 20KB, match that width-to-height ratio during cropping rather than cropping to a square or a very different rectangle, since a squashed or oddly shaped signature can look "miniature" or unclear, which several exam notices list as a reason for rejection.
Tools for this
Frequently asked questions
Why is my 20KB photo so blurry?
It was likely compressed at a large pixel size. Crop and resize the image down first, then compress; the same 20KB target looks much sharper on a smaller starting image.
Is 20KB enough for a clear signature?
Yes, a well-cropped signature on plain white paper usually compresses cleanly to 20KB or less, since most of the image is plain background with only a thin ink line.
Should I use JPG or PNG for a 20KB image?
JPG almost always compresses a photograph or signature scan smaller than PNG at similar visual quality, so use JPG unless a specific form requires PNG.
What pixel size should I resize to before compressing?
Match whatever pixel dimensions your specific form specifies. If none are given, a small, tightly cropped image, similar in scale to a signature or a small ID photo, compresses most cleanly to 20KB.
Can a full face photo look sharp at 20KB?
It will be visibly softer than a larger file size, since a real face carries a lot of fine detail, but a tightly cropped, small photo can still look acceptable for most form requirements at this size.
Sources
- MDN Web Docs, Image file type and format guide (checked 2026-09)
- Staff Selection Commission, CGL 2026 Notice (signature 10-20KB) (checked 2026-09)
Rules and limits change. Always check the latest official notification or portal before you submit a form.