Why 20 KB is a tough target
Twenty kilobytes is about 20,000 bytes. An uncompressed 12-megapixel photo would need 36 million bytes, so getting under 20 KB requires shrinking the data by a factor of nearly 2,000. That is only possible by reducing both the number of pixels and the quality setting. This tool does both automatically: it first searches for the highest JPG quality that fits at the current size, and only if the lowest acceptable quality is still too big does it scale the image down, repeating until the result fits.
Signatures
Signature scans compress very well because they are mostly white with thin dark lines. For best results:
- Crop tightly around the signature with the crop tool so there is little empty paper.
- Use dark ink on white paper and scan or photograph in good, even light.
- Aim for about 400 × 150 pixels, which is legible and easily fits under 20 KB.
Small photos
For a face photo, a size around 300 × 400 pixels fits comfortably within 20 KB at decent quality. Plain, light backgrounds use fewer bytes than busy ones, and a well-lit photo compresses better than a dark, noisy one taken indoors at night.
Checking the result
After compression, the results list shows the final file size and pixel dimensions. Compare these with the form’s requirements. Many systems state both a maximum size (for example 20 KB) and a minimum size (for example 10 KB); if your file is unexpectedly tiny, raise the target slightly so it does not fall below the minimum.
PNG and HEIC inputs
Signature scans are often PNG and phone photos are HEIC. Neither can be compressed to a size target directly, so the tool converts them to JPG automatically, or to WebP if a PNG has a transparent background. Most forms with a 20 KB limit expect JPG anyway; check the accepted file types listed on the form.
Other common limits
If your form allows more, use a larger target for better quality: 50 KB for photos and 100 KB for documents are common alternatives.