Compress a PDF to under 100 KB
Get a PDF under the 100 KB cap that government and university upload forms insist on. The quality search runs on your device, so retries are free.
- Runs in your browser
- Files are never uploaded
- Free, no account
Where the 100 KB rule comes from
100 KB is not a considered choice about legibility. It is a default that spread through government and university upload software in the era when a scanned document was stored as a BLOB in a database column, and it has survived long after the reason for it disappeared. You will meet it on visa applications, scholarship portals, exam registration systems, tender submissions and public-sector recruitment sites.
Because it is arbitrary, there is no point arguing with it. The only useful question is how to spend 102,400 bytes as well as possible.
What 100 KB buys you, page by page
| Pages | Bytes per page | Realistic outcome |
|---|---|---|
| 1 | ~100,000 | Good. A colour ID scan stays clearly readable at around 120–150 DPI. |
| 2 | ~50,000 | Fine for text. Photographs start to soften. |
| 4 | ~25,000 | Body text still legible; small print and signatures blur. |
| 10 | ~10,000 | Visibly degraded. Consider submitting fewer pages instead. |
| 25+ | ~4,000 | Below the useful floor — the file structure alone eats a meaningful share of the budget. |
The tool rolls unused budget forward: a page that is mostly white space finishes well under its share, and everything it did not use is handed to the next page. That is why a covering letter followed by a dense scan often comes out better than the flat arithmetic above suggests.
Getting a better 100 KB
- Submit only the pages that were asked for. This is the single biggest lever. Two pages at 100 KB look twice as good as four. Use Extract PDF pages first.
- Turn on grayscale if the document has no meaningful colour. A black-ink scan photographed in colour carries a full chroma channel it does not need — dropping it typically frees 10 to 25 per cent.
- Crop the margins. Phone scans often include desk, hand and shadow. Fewer pixels of noise means more bytes for the text.
- Let the resolution stay automatic unless the result is unreadable. Forcing 200 DPI at a 100 KB target simply pushes the JPEG quality down until the page looks worse than it would have at 110 DPI.
Reading the per-page table
Every run shows the JPEG quality and scale factor each page settled on. Use it as a judgement aid rather than a score:
- Quality 70 and above — indistinguishable from the original at normal zoom.
- Quality 45–70 — fine on screen, slight softening around small text when printed.
- Quality 20–45 — visible blocking in flat areas. Acceptable for a form, not for anything that has to be read carefully.
- Scale below 100% — that page could not fit even at the lowest quality, so it was reduced in resolution too. Check it before submitting.
Why the iteration is the whole point
Hitting an exact byte target is not a single operation, it is a search. Each page here is rendered once and then re-encoded up to nine times at different quality settings until the largest one that fits is found. On your laptop that is a few hundred milliseconds; on a server it is nine encodes billed to someone, per page, per attempt — which is precisely why upload-based compressors offer you "low, medium, high" and then let you guess.
The same asymmetry applies to retries. Not happy with the result? Change one setting and run it again, as often as you like. There is no daily count because there is nothing counting.
Questions
Why do so many forms ask for 100 KB?
It is a legacy default in a lot of government and university upload software — often a per-field database column limit rather than a considered choice. It has nothing to do with how readable the document is, which is why hitting it usually costs visible quality.
Will my scanned ID still be readable at 100 KB?
A single-page scan usually survives, because the whole budget goes to one image. Anything past about four pages at 100 KB starts to look rough. The result panel shows the exact JPEG quality each page ended up at, so you can judge it before you submit.
What if the file is already under 100 KB?
We tell you and recommend uploading it untouched. Compressing an already-small PDF only removes quality — there is no reason to run it.
Does the text stay searchable?
No. Reaching a hard byte target means re-rendering each page as a JPEG, so the text layer is gone. If searchable text matters more than the exact size, use our lossless compression instead.
Is there a page limit?
No. The work happens on your machine, so a 200-page document is only a matter of time and memory, not a plan tier.