What 100 KB buys you
For one page, quite a lot. A phone photo of a one-page certificate went from 1.9 MB to 91 KB in our tests, at about 106 DPI. At that resolution the text is clean on a phone and on a laptop, and a printout reads fine. The same certificate from a 300 DPI office scanner needed only 72 KB.
For more pages, it gets tighter fast:
| Scanned or photographed pages | Under 100 KB? |
|---|---|
| 1 | Yes, and it looks clear |
| 3 | Only just: 83 KB in our tests, readable up close |
| 5 | No. The smallest readable version was 151 KB |
The rule behind the table: a scanned page needs about 30 KB to stay readable at all, about 45 KB to read comfortably and about 90 KB to look clean. Divide 100 by those and you know what to expect before you press the button. Two pages, for example, land around the comfortable middle.
Why your file is so big to begin with
Phones take 12-megapixel photos or more, and a scanning app keeps all of them. That’s around 360 DPI on an A4 page, more than a print shop asks for. An upload form only needs the page to be readable on a screen, so most of those pixels go nowhere. We bring the photos down to what the limit allows and leave the text alone.
If the PDF came from Word or a website rather than a camera, it’s mostly text, and 100 KB holds many pages of it.
Making a longer document fit
When a four- or five-page scan has to go under 100 KB, the honest options are fewer pages or more uploads:
- Remove blank pages catches the empty backs of double-sided scans. They cost as much as written ones.
- Extract PDF pages keeps only the pages the form asks for, like the first page of a statement and the page with the total.
- Split PDF by size cuts it into parts under 100 KB if the form takes several files.
If you have a choice of limit, the 200 KB page gives three phone-photo pages a much easier read.
Before you upload
The result screen shows the exact size and confirms it’s under 100 KB. On a phone, the Files app shows the size too (on an iPhone, touch and hold the file, then Get Info), so you can check it against the form’s own number.
Checked against the tool on 22 October 2026. How we write and test these guides