Make a signature image fit 4KB to 30KB without breaking the strokes

Signature upload rules are annoyingly specific because the file is tiny and the reviewer still needs to see every stroke. A 4KB to 30KB range leaves very little room for messy scans, shadows, and huge white margins.

The fastest fix is to clean the image shape before touching JPG quality.

Crop the canvas tight

Most failed signature files are mostly blank paper. That blank area still has pixels, and pixels cost bytes.

Crop the image so the signature has a small amount of breathing room around it, but not a full sheet of paper. A tight crop gives the signature more of the available file budget.

Keep the background simple

Portals usually expect a light or white background. Shadows, notebook lines, folds, yellow lighting, and scanner dust all increase file size because JPG has to encode that texture.

Before exporting, aim for:

• Dark ink or pen strokes.
• A light, even background.
• No table, page edge, or phone shadow.
• No decorative borders.

If the signature is too pale, increasing contrast is better than extreme compression.

Resize for the rule, not for your screen

A signature does not need phone-camera dimensions. If the portal gives pixel dimensions, use those. If it only gives a KB range, start with a compact width such as 300px to 600px and check readability.

The goal is not the sharpest file possible. The goal is a valid upload where the signature still looks like a signature.

Do not fall below the minimum

Many exam portals reject files under 4KB. That surprises people because smaller usually sounds better.

If your file is below the minimum, increase dimensions slightly or export at a higher JPG quality. Do not add random noise or borders. That can make the signature look tampered with.

Export as a real JPG

Renaming a PNG to .jpg does not convert it. Some portals inspect the actual file type, not only the extension.

Use the Signature Under 30KB tool to create a real JPG signature in the target range. It runs locally in the browser and validates the output before you download it.

A quick rejection checklist

If the upload fails, check these in order:

• The file is between the minimum and maximum KB values.
• The file is actually JPG.
• The signature crop is not too loose or too tight.
• The background is plain and light.
• The strokes are dark enough after compression.
• The filename is simple, such as signature.jpg.

Most signature upload problems are small mismatches. Fix the rules one by one instead of repeatedly compressing the same bad source image.