Compress an Image to Under 100 KB

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100 KB is the usual ceiling for identity document uploads on banking, tenancy and verification portals. It is enough for a readable document scan, if the pixels are spent on the document rather than on the desk around it.

What to expect

Can every image reach 100 KB?

An identity card or a single page document reaches 100 KB while staying readable, provided it is cropped to the document and sized to roughly 1400 px on the long edge. That is the point where text keeps about 20 pixels per line, which is the floor for staying legible after compression.

KYC and bank onboarding

Identity verification uploads are commonly capped at 100 KB per document.

Tenancy and employment checks

Right to work and right to rent document uploads, where a human reviews the result.

Visa supporting documents

Per file limits on immigration portals, separate from the overall application size.

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

About 1400 px on the long edge for a document, cropped to its edges.

Then compress to the limit

Quality comes down until the file is under 100 KB, and stops there. Aim just under the limit rather than far below it: unused bytes are quality discarded for nothing.

Resize first Compressing an ID scan to 100KB and keeping it readable

Need a different size?

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

Under 20 KB Under 50 KB Under 200 KB Under 500 KB Under 1 MB Any size

Common questions

Questions answered.

My scan is under 100 KB but was rejected as unreadable. Why?

You probably compressed a large image rather than resizing it first, or you aimed far below the limit. Crop to the document, resize the long edge to about 1400 px, then compress to just under 100 KB rather than to 40 KB.

Should I aim well under the limit to be safe?

No. Aim just under it. Every unused byte is quality discarded for nothing, and identity scans are rejected by reviewers for being unreadable far more often than they are rejected by portals for being close to the limit.

Is a phone photo or a scanner better?

Often the phone, in even daylight. Scanners capture paper texture and dust as fine random detail, which is the most expensive thing to compress. Keep the phone parallel to the document and avoid flash.

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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