Compress an Image to 100 KB

1. Leave the target where it is. The panel opens in target mode with 100 KB already typed in, so there is nothing to set unless the form you are filling in asks for a different number.
2. Choose the image on your device. Drop a JPEG, PNG or WebP onto the panel above, or press Browse files. The file stays on your machine — there is no transfer step to sit through.
3. Press Compress image. Your device encodes the picture and measures the real byte length, up to 8 times, keeping the best-looking version that still fits under 100 KB.
4. Download the file and check the number. The panel prints the size it reached. If even the smallest encode overshoots you are told the smallest size that image can reach, rather than handed a file that misses the limit.

A 100 KB ceiling is almost never an aesthetic decision. It comes from the system on the other side: a recruitment portal storing photographs for hundreds of thousands of applicants, an examination board with a fixed field size, a government service built against a database column that was sized years ago and never revisited.

Examination and recruitment portals are the most common source of it. They typically ask for a passport-style photograph somewhere between 20 KB and 100 KB, and a scanned signature between 10 KB and 20 KB, with the file rejected outright above the stated figure. University applications, visa services and insurance claim uploads use the same pattern. In every case the number is a hard ceiling rather than a suggestion, which is why landing just underneath it is the only useful behaviour.

No image encoder takes a byte count as an instruction. You can ask a JPEG encoder for quality 62; you cannot ask it for 102,400 bytes, because the size that comes out depends on the picture — a plain studio background and a photo of a forest produce wildly different files from the same setting.

So the tool measures rather than predicting. It encodes at a probe quality, reads the real length of the result, and bisects the quality range from there, up to 8 times, keeping the best-looking version whose size still fits. What you download is the largest file that stays under your number. It is reported back to you in the panel next to the original size, so you can check it before you submit anything.

There is a floor to what any image can be compressed to, and it is set by how many pixels it has. A 12-megapixel photograph has twelve million pixels to describe; squeezing that into 100 KB leaves well under a tenth of a bit per pixel, and the result is visibly blocky whatever the encoder does.

When that happens the tool tells you the smallest size it could actually reach for your file. The fix is to reduce the dimensions and try again — around 1000 to 1200 pixels on the long side is a comfortable home for a 100 KB photograph, and it is more than enough for any form that displays a headshot. Resize it first, then come back here.

A photograph is continuous tone, so lowering the JPEG quality is the right lever and the search above finds it in a few encodes. A scanned signature is the opposite: black ink on white paper, two colours doing almost all the work.

If that scan is a PNG there is nothing to turn down: the PNG encoder in this page is lossless and has no quality setting, so the same bytes come out however many times you run it. A signature scan is usually small enough that it fits anyway. When it does not, the answer offered is WebP — which reaches the number at the full picture size — rather than quietly handing you a smaller picture. If the scan is a JPEG, consider raising the scanner contrast instead: clean white paper compresses far better than a grey, speckled background.

The number in the panel above is editable, so any target from 10 KB up to 20 MB works on this page. There is also a 200 KB version, which is the other limit forms ask for most often and gives a full-size photo noticeably more room, and the main compressor if you would rather work with a quality slider than a byte target.