Compress Signature to 30KB | MiniPx — Free, Fast & Private
If you are looking for 30 KB, you are almost certainly uploading a signature, not a photograph. That is the number’s real home: it is the ceiling of the signature band on several Indian recruitment portals.
| Form | Signature size | Dimensions |
|---|---|---|
| SSC CGL / CHSL | 10–30 KB | 140 × 60 px |
| RRB NTPC / Group D | 10–30 KB | 140 × 60 px |
| IBPS PO / Clerk | 10–20 KB | 140 × 60 px |
Two portals sit outside this pattern and are worth naming so you do not waste a submission. UPSC wants a triple signature at 20–100 KB and 350–500 pixels — a different file entirely, covered on our UPSC page. PAN / NSDL goes tighter still, at 2–10 KB, which the 20KB compressor handles better.
Why signatures are harder to compress than photographs
It seems backwards. A signature is a few strokes of ink on white paper — far less information than a face — so it ought to compress to nothing. In practice it fights back, and the reason is worth understanding because it tells you which setting to reach for.
JPEG compresses by discarding high-frequency detail: the fine, rapid changes between neighbouring pixels. A photograph is mostly smooth gradients, so it loses that detail gracefully. A signature is almost entirely high-frequency — every stroke is a hard black-to-white edge. Push JPEG quality down and the compressor cannot find anything gentle to throw away, so it attacks the edges themselves. You get ringing: faint grey halos and speckles around each stroke, on what should be clean white paper. Push further and thin strokes break into dashes.
So the lever that actually works on a signature is cropping and dimensions, not quality. Halving the width removes three quarters of the pixels and takes the file size with it, while every remaining stroke stays crisp. Dropping quality from 70% to 40% saves far less and visibly damages the ink.
Getting a clean scan in the first place
Half of all rejected signatures are lost before any tool is opened. Sign on plain white unlined paper with a black or dark blue pen — a ballpoint that skips will scan as a broken line. Photograph it from directly overhead in even daylight, not under a single ceiling bulb, which casts a grey gradient across the page that compresses badly and can read as a tinted background.
Then crop tightly, right up to the ink. This matters more than any compression setting. A signature photographed on a full A4 sheet is perhaps 5% signature and 95% empty paper, and you are paying file size for all that emptiness. Crop to the strokes and the file often lands under 30 KB before you compress anything at all.
The 140 × 60 pixel question
SSC, RRB and IBPS all specify 140 × 60 pixels. That is a landscape strip, roughly 2.3 : 1, and it is genuinely small — about the size of a large button on screen. Some portals enforce it strictly; others accept anything of roughly the right shape.
The practical approach: crop to about a 2.3 : 1 landscape shape first, so nothing gets squashed, then set the width. At 140 pixels wide a JPEG signature usually lands between 4 and 12 KB — which, note, is below the SSC 10 KB floor if you are unlucky. If that happens, raise the quality rather than the dimensions: you want to add file size without breaking the specified size.
Why your signature upload was rejected
“File size not in range.” Check the floor, not just the ceiling. SSC wants 10–30 KB, and a tightly cropped signature at low quality can easily come out at 6 KB. That fails. Raise quality until you are inside the band.
“Background not white.” Usually a lighting problem, not a paper problem. Uneven light leaves one side of the page grey. Reshoot in daylight, or crop away the shaded region.
“Signature not clear.” Over-compression has broken the strokes. Go back to a larger crop and a higher quality, and cut the file size by reducing dimensions instead.
It uploaded but looks wrong on the printout. You saved a PNG. PNG stores every anti-aliased edge pixel exactly, and handwriting is nothing but anti-aliased edges, so PNG signatures are routinely three to four times larger than the JPEG equivalent. Use JPEG here.
Everything runs in your browser. Your signature is never uploaded to a server, which matters rather more for a signature than for a holiday photo — see the full signature guide for the per-exam specifications.