Compress an Image to Under 20 KB

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20 KB is one of the tightest limits still in common use, and it is nearly always a signature box or a small photo field. Drop your image in and it is compressed down to fit.

What to expect

Can every image reach 20 KB?

A cropped signature or a small head and shoulders photo reaches 20 KB comfortably. A full page document scan will not, at any quality setting, because a page of text needs enough pixels to resolve the letters and below that threshold the text stops being readable rather than merely soft.

Signature fields

Exam and recruitment portals commonly cap the signature image at 20 KB, separately from the photograph.

Thumbnail uploads

Older systems that store a small avatar or list thumbnail rather than a full image.

Legacy government forms

Limits set when storage was priced very differently, and never revised since.

The part people skip

Pixels first, then quality.

File size follows from pixel count. Squeezing a 4000 pixel wide photo down to a small target asks the encoder to describe twelve million pixels in a few kilobytes, and it will, badly. Reduce the dimensions first and the same target becomes easy.

Crop away what is not the subject

Paper around a signature, desk around a document, background around a face. Empty space costs pixels like anything else.

Resize to what is needed

Around 600 x 200 px for a signature, or 300 x 400 px for a photo.

Then compress to the limit

Quality comes down until the file is under 20 KB, and stops there. Aim just under the limit rather than far below it: unused bytes are quality discarded for nothing.

Resize first How to compress an image to 20KB

Need a different size?

Pick the limit you actually have to meet, or set any figure you like on the main compressor.

Under 50 KB Under 100 KB Under 200 KB Under 500 KB Under 1 MB Any size

Common questions

Questions answered.

Can a document scan fit in 20 KB?

Not as a readable image. Text needs roughly 20 pixels of height per line to survive compression, and a full page at that resolution is far larger than 20 KB. If the form is asking for a document, check whether it accepts a PDF, where text stays as text and the file can be tiny.

Why is my scanned signature so large to begin with?

It was probably scanned at 300 or 600 DPI across a whole sheet of paper, which is millions of pixels to describe a few pen strokes. Crop tight to the signature first and the target stops being a struggle.

Should I use JPEG or PNG for a signature?

Try PNG. A high contrast signature has very few distinct colours, which is the case PNG compresses efficiently, and it avoids the grey smearing heavy JPEG compression leaves around dark strokes on white.

How does it hit an exact size?

It compresses, measures the result, and narrows in on the quality setting that lands just under your target rather than far below it. Stopping at the first setting that fits means you keep as much quality as the limit allows, instead of always getting the harshest setting.

Should I resize before compressing?

For a tight target, yes, and it is the single biggest thing you can do. File size follows from pixel count, so reducing the dimensions first means the quality setting does not have to work as hard. Compressing first and resizing afterwards throws away quality and then throws away the pixels you paid for it with.

Is my image uploaded anywhere?

No. The compressor runs entirely inside your browser. Your image never leaves your device, there is no account, and there is no queue. That matters most for the files these limits usually apply to, which are identity documents, signatures and photographs of your face.

What if the target cannot be reached?

You get the smallest version that could be produced. When a target is impossible it is usually because the image has more pixels than the target has bytes to describe them, and the fix is to reduce the dimensions rather than to compress harder.

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