Compress Image to 100 KB
Shrink any photo to 100 KB or less without leaving this page. The tool finds the highest quality that still fits 100 KB, so you get the sharpest version of your image that the limit allows.
Where the 100 KB limit appears
One hundred kilobytes is the usual ceiling for scanned documents — mark sheets, certificates, identity proofs, experience letters — and for photographs on portals less strict than exam boards. It is a comfortable limit: most single-page scans fit at readable quality without any dimension change at all.
The dpi decision that determines everything
Scanner resolution controls the pixel count, and the pixel count controls how far 100 KB stretches. For an A4 page:
| Scan resolution | Pixels (A4) | Text legibility at 100 KB |
|---|---|---|
| 100 dpi | 827 × 1169 | Fine for large print, weak for small |
| 150 dpi | 1240 × 1754 | Good — the practical sweet spot |
| 200 dpi | 1654 × 2339 | Acceptable, slightly soft |
| 300 dpi | 2480 × 3508 | Mushy — too many pixels for the budget |
The counter-intuitive part: scanning at higher resolution makes the compressed result worse, because the same 100 KB must now describe four times as many pixels. If the document is already scanned at 300 dpi, reduce the dimensions here rather than settling for a lower quality setting.
Colour, greyscale and where the bytes go
JPEG stores brightness and colour separately, and it already discards much of the colour information because eyes are less sensitive to it. A colour scan of a black-and-white document still spends real bytes recording that the paper is slightly cream and the ink slightly blue.
Scanning in greyscale typically cuts the file by about a third before compression begins, leaving that budget for sharper text. The exception is any document where colour carries meaning — a stamp, a seal, a coloured signature, a photograph on an identity card — where colour should be kept.
Multi-page documents
When a form wants several pages and caps each at 100 KB, process them individually at the same settings so they look consistent. When it wants one file containing several pages, that is a PDF job rather than an image job — combine the pages into a PDF first, then compress the PDF with a PDF tool. Compressing each page image to 100 KB and then combining them produces a much larger PDF than necessary.
Checking legibility properly
View the result at 100% zoom, not fitted to the window. A page that looks fine scaled down to fit your screen can be unreadable at full size, which is how the reviewer will open it. Pay attention to the smallest text on the page — usually a registration number, a date or a footnote — because that fails first.
If the small text has gone, the answer is more pixels and lower quality rather than the reverse: text survives dimension changes better than it survives aggressive quantisation.
When the scan is a photograph of a document
Phone photos of documents carry problems a scan does not: uneven lighting, a grey cast from shadow, perspective distortion, and camera noise across the paper. That noise is random variation, which is the most expensive thing JPEG can encode — it can easily double the compressed size versus a clean scan of the same page.
Photograph the page flat in even daylight, crop tightly to the paper edges, and if your phone has a document-scanning mode, use it. It flattens perspective and whitens the background, which both improves legibility and removes the noise that was costing you kilobytes.
Questions
Is 100 KB enough for an A4 scan?
Yes, if the scan is around 150 dpi rather than 300 dpi. At 300 dpi the page has four times as many pixels to encode within the same 100 KB.
Should I use JPG or PNG for a 100 KB document?
JPG. A PNG of a scanned page is usually 500 KB or more, and PNG ignores quality settings, so it cannot be tuned down to a byte target.
My file is already 80 KB — will this make it worse?
No. If it already fits under 100 KB the tool returns it at high quality rather than compressing it further.
Why is my phone photo of a page so much bigger than a scan?
Camera noise and uneven lighting add random variation across the paper, and random variation is the most expensive thing for JPEG to store. A document-scanning mode removes most of it.
Can I compress a PDF to 100 KB here?
No — this tool works on images. Export the page as JPG first, or use a PDF compressor for multi-page files.