Compress an image to 20 KB

20 KB is the size forms ask for when they mean a signature

Exam boards and government portals nearly always split the upload in two: a passport photo, usually allowed 20 to 50 KB, and a signature, usually capped at 20 KB or even less. The signature is the one that catches people out, because a photo of ink on paper taken with a modern phone starts life somewhere around two megabytes — a hundred times over the limit.

The form will not explain any of this. It will simply refuse the file, often after you have filled in everything else. Setting the target to 20 KB here and re-uploading is usually the whole fix.

Signatures fit easily. Photos need more care.

A signature is mostly white paper with a few dark strokes, which is exactly the kind of picture that compresses well. Getting one to 20 KB while keeping the strokes sharp is straightforward.

A face photo is harder. Skin tones and background detail carry far more information, so at 20 KB some softness is unavoidable. If the form allows 50 KB for the photo, use 50 for the photo and 20 only for the signature — there is no prize for going smaller than the limit.

Crop before you compress

Most rejected signature uploads are mostly empty desk. Crop tightly to the ink first, then compress. Removing the wasted area does more for the file size than any compression setting, and it does not cost you a single pixel of the part that matters.

The picture never leaves your phone or computer

Compression happens inside your browser. Your photo, your signature and your identity documents are not uploaded to any server and are not stored anywhere — which is the point, given what these forms usually ask you to attach.

Questions people actually ask

Can a photo really be compressed to 20 KB?

Yes, though how good it looks depends on the picture. Signatures and simple scans reach 20 KB while staying sharp. Face photos will lose some fine detail at that size. Check the preview before submitting.

What size do exam forms usually want?

Most ask for a photo between 20 KB and 50 KB and a signature at 20 KB or under. The exact numbers are printed in the instructions on the upload page, and they vary between boards.

Will it change the dimensions of my image?

The tool works on file size, not on the width and height you see. If your form also specifies pixel dimensions, crop the image to those dimensions first, then compress it here.

Is my photo uploaded to a server?

No. Everything runs in your browser on your own device. Nothing is sent anywhere, nothing is saved, and nobody else sees the file.

Which formats can I use?

JPG and PNG both work. For photographs and signatures, JPG usually reaches a small size more cleanly than PNG.

Can I do this on my phone?

Yes. The page works in a mobile browser, which helps because the signature you need is usually a photo you have just taken.

Should I crop before or after compressing?

Before, always. Cropping removes background that the encoder would otherwise spend your size budget on, so a tightly cropped head-and-shoulders photo at 20 KB looks dramatically better than a full-frame one at the same size.

Should I use JPG or PNG for a form photograph?

JPG, unless the form explicitly demands PNG. JPG compresses photographic detail far more efficiently, so at a fixed kilobyte target a JPG will always look better than a PNG of the same subject. PNG only wins on flat graphics such as a scanned signature.

What is the smallest a usable passport photo can be?

Around 20 KB for a tightly cropped head-and-shoulders JPG at roughly 300 by 400 pixels. Below that, skin tones start to band and the face reads as blocky. If a form demands less than 20 KB, crop harder rather than compressing harder.

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