What it takes to reach 10 KB
Ten kilobytes is a very small file. A phone photo is usually a few megabytes, so it has to lose more than 99% of its weight. In the test, the 2000 x 1333 photo came down to 824 x 549 pixels at JPEG quality 34, and the 12 MP photo ended at 805 x 537. Quality alone could not get there, so the tool also shrank the pixels.
At this size a photo still works as a small form photo or a thumbnail. Fine detail goes first: small text in a scanned page, hair, leaves and fabric.
| Test image | Original | Result | JPEG quality | Pixels | Time |
|---|---|---|---|---|---|
| Photo | 694 KB | 9.9 KB | 34 | 824 x 549 (from 2000 x 1333) | 1.4 s |
| 12 MP photo | 1.81 MB | 10.0 KB | 35 | 805 x 537 (from 4000 x 2667) | 4.9 s |
| Screenshot | 46 KB | 9.9 KB | 35 | 878 x 494 (from 1600 x 900) | 760 ms |
| Illustration | 94 KB | 9.9 KB | 37 | 799 x 799 (from 1200 x 1200) | 1.5 s |
Test images are synthetic files made by this project: a 2000 x 1333 landscape photo, a 1600 x 900 interface screenshot and a 1200 x 1200 transparent illustration. The 12 MP photo is the same photo scaled up to 4000 x 2667, the size a phone camera saves. Quality is lowered first and the image is only scaled down when quality alone cannot reach the target. A JPEG that is already under the target is left as it is. Timings: one thread of WebAssembly on Node v22.23.4, Intel(R) Xeon(R) Processor @ 2.10GHz, 2 cores, measured 2026-10-31. Other devices will differ.
Where 10 KB limits show up
Government portals, exam forms and older job sites often cap signatures and small photos at 10 KB or a little more. A signature scan has few details and fits easily. A full photo needs heavy shrinking, which is why the result looks soft when you zoom in.
If your form also gives a minimum size, a pixel size or a DPI value, use the exam photo and signature resizer. It handles the minimum, the pixel size and the DPI as well as the upper limit.
Get a sharper result at 10 KB
- Crop to what matters first, such as your face and shoulders or just the signature. The crop tool keeps everything on your device.
- Resize to the pixel size the form asks for, or to about 300 to 400 pixels on the long side if it does not say. The resize tool does this in one step.
- Then compress here. With fewer pixels to store, each one gets more of the 10 KB.
The screenshot in the table shows the same effect from the other side: it kept 878 x 494 pixels at quality 35, because flat areas of colour cost very little.
Which format to choose
JPEG is the default here because forms accept it. WebP gets a little more detail into the same size, but many upload forms refuse it. Same format keeps a PNG as a PNG, and a PNG can only shrink by losing pixels, so it usually looks worse at 10 KB than a JPEG.
Check before you upload
Open Compare on the result and look at it at 100%. If the face or the signature looks blocky, crop tighter and run it again. Running the same image again does not use more of the daily limit.
Questions
Why does my photo look blurry at 10 KB?
The photo had to lose most of its pixels to fit. Crop to the face or the signature first and the result will hold more detail.
Will the file be exactly 10 KB?
It will be just under 10,000 bytes. That also passes forms that count 1 KB as 1024 bytes.
Does this work for a signature?
Yes. Signatures compress well, and most fit under 10 KB with little visible change.