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Compress an image to 40 KB

Forty kilobytes sits between the strict exam sizes and the common 50 KB limit.

  • Nothing is uploaded. Your browser does the compression, so the file stays on your device.
  • Lands under the real limit. We aim a little below it, so the upload goes through first time.
  • Fast. A 30 second 1080p clip fits into 10 MB in about two seconds on a desktop.
Where are you sending it?

Custom size 40 KB. We aim for 39 KB, a small safety margin so the file never lands just over.

Sent to our servers: 0 bytes. It all happens in this tab.

When you need 40 KB

Forms that allow up to 40 KB for a photo, and email signatures that should stay light.

What to expect

A headshot keeps about 450 pixels of width. A small logo stays crisp.

How big a picture fits in 40 KB

Rough pixel sizes at good quality. The tool checks the real result, so treat these as a guide.

What it isAbout this many pixels
Detailed photo (landscape, crowd)360 x 240
Typical photo or headshot440 x 290
Scan, signature or screenshot of text760 x 510

How we hit the number

We try the highest quality that fits. If the picture still will not fit even at a lower quality, we reduce the pixel size a step at a time until it does. Photos are saved as JPEG by default, which every form accepts. You can switch to WebP or PNG with the format menu.

The target we aim for is 39 KB, which is 1 KB under 40 KB, so the file is not turned away over a few bytes.

Questions people ask

Why does my result come out at 38 KB and not 40?

We leave a small margin so the file is not rejected for a few bytes. A form may count a kilobyte as 1,024 bytes or 1,000, and the margin covers both.

Related

Limits change. We link the official page wherever there is one, and the safety margin means a small change is unlikely to matter. Last updated 2026-11-09.