How to Compress a Signature Image for an Online Form

Sign in dark ink on plain white paper and scan or photograph it straight-on with even lighting. A clean, high-contrast source compresses far better than a shadowed phone snap.

Crop tightly to the ink so there is little white space around the signature — this is the single biggest factor in hitting a small KB target while staying sharp.

Signature caps are often 10–20 KB. Because a signature is mostly white space with thin dark strokes, it stays crisp even at those sizes. Set the exact limit and export as JPG (or PNG if the form requires transparency or asks for it).

If the compressed signature looks speckled, increase contrast in the source scan or crop tighter, then re-run. Avoid screenshots of a signature — they add noise and increase file size.