Compress an image to 20 KB

Get a clear signature under 20 KB

1. Sign in dark blue or black ink on plain white paper.
2. Photograph it in daylight, straight from above, with the signature filling most of the frame.
3. Choose the photo above, keep the target at 20 KB and select Compress images.

A signature has lots of white space and very little detail, so it compresses well. A 4 MB phone photo will typically come down to 10 to 20 KB while staying readable.

If the form also asks for pixel dimensions

Some forms say, for example, “140 × 60 pixels, 10 to 20 KB”. In that case use the photo and signature resizer, which crops or fits the image to the exact dimensions and the size range in one step.

Common reasons uploads are rejected

• The file is a PNG or HEIC when the form wants JPG. This tool always saves JPG by default.
• The image is smaller than the minimum size, such as 10 KB. Use a slightly larger target, such as 18 KB.
• The signature is faint. Use darker ink and better light rather than editing the photo.

How to photograph a signature for a 20 KB limit

1. Sign on plain white paper with a black or dark blue ballpoint or gel pen. Avoid pencil and light blue ink, which fade after compression.
2. Sign a little larger than usual, inside a box roughly 7 cm wide and 3 cm high.
3. Place the paper on a flat surface near a window. Hold the phone directly above it so the edges of the paper look straight, not slanted.
4. Turn off the flash, which can leave a bright patch, and tap the screen to focus on the ink.
5. Crop the photo close to the signature in your phone's editor, leaving a small white margin, then compress it here.

Why signatures compress so well

A signature is mostly white paper with a few dark lines. JPG compression handles large plain areas very efficiently, which is why even a tightly cropped high-resolution signature usually fits under 20 KB without visible loss. Shadows, paper texture and a grey background make the file larger, so good light helps more than any setting.

Thumb impressions and small photos

Thumb impressions follow the same steps: use a stamp pad, press the thumb once on white paper, photograph it straight on, and crop closely. Faces are harder: at 20 KB a portrait loses detail quickly. If a form allows a larger size for the photo, such as 50 KB, use compress to 50 KB for the photo and keep 20 KB for the signature.

Checking before you upload

• Open the compressed file and zoom in: every letter of the signature should be readable.
• Check the file type is .jpg if the form asks for JPG or JPEG; they are the same format.
• Check the size shown under the result is inside both the minimum and the maximum the form allows.
• If the form also gives pixel dimensions, such as 140 × 60, use the photo and signature resizer.

Questions

Related tools

• Photo and signature resizer
• Compress image to 50 KB
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