How to compress a PDF to 100 KB
- Tap Choose PDF above and pick your file (or drop it on the box).
- The Target size (KB) is already 100. Change it if your portal states a different limit.
- Tap Compress PDF. The gauge shows the result against your limit; most files take a few seconds.
- Tap Download compressed PDF. Open it and check every page is readable before you upload it.
What fits in 100 KB: measured
| Document | Original | At 100 KB | Images kept at |
|---|---|---|---|
| 2-page phone scan | 6.34 MB | 96 KB | 751 px |
| Fillable form with a photo (4 fields) | 3.18 MB | 89 KB | 1012 px |
| 2-page letter printed from Chrome, with a photo | 2.56 MB | 90 KB | 939 px |
| Colourful certificate scan | 1.82 MB | 99 KB | 1091 px |
| 10-page phone scan | 34.12 MB | Not reachable with readable text (smallest: 276 KB) | — |
Test files: the documents above, made by us from phone photos and printed pages (the form has four fillable fields). Desktop Chromium on our test server, 27 October 2026; each took under 6 seconds. "Images kept at" is the long side of the page images after compressing. Every result kept its text and form fields. Sizes in decimal units (1 KB = 1,000 bytes), as the tool shows them.
The form shows how the compressor works: at 89 KB its typed labels and four fillable fields are exactly as they were, because only the embedded photo was shrunk. Scans are all image, so the 2-page scan's pages went down to 751 pixels on the long side: normal print stays readable, small print blurs. The 10-page scan can't reach 100 KB with readable pages at all: about 10 KB per page is too little.
How many pages fit in 100 KB
| Pages | Budget per page | What to expect |
|---|---|---|
| 1 | 100 KB | A clear, readable page |
| 2 | 50 KB | Readable at normal print size; small print soft (our test: 751 px) |
| 3–4 | 25–33 KB | Large text only; check every page |
| 5 or more | 20 KB or less | Usually unreadable: remove pages, or ask whether the limit is per page |
From our measurements, about 50 KB per page kept 751-pixel pages (readable at normal print size) and about 100 KB per page kept 1091 pixels. Rows below 50 KB per page are estimates; always check the result.
If it can't reach 100 KB
When the text version is still over the limit, PixKB tells you the smallest size it reached and why. If rebuilding every page as an image would get closer, it offers Rebuild pages as images to reach the limit: pages look the same, but text can no longer be selected and fillable fields become flat. If even that wouldn't help (as with our 10-page scan), it says so instead of offering it. Then remove pages, or make the PDF again from photos with JPG to PDF in Document mode, which turns pages black and white and often looks crisper at small sizes.
Common mistakes
- Including pages the portal didn't ask for. A blank back side or an extra copy halves every other page's share of the limit.
- Not cropping scans. A table edge or the background around the paper uses part of the limit. Scanner apps crop automatically; see scanning a document for upload.
- Compressing an already-compressed copy again. Start from the original PDF each time you try a different limit.
- Uploading without checking. Open the result and zoom in on the smallest print before you submit.
- Splitting the limit wrong. If the portal has one limit for several uploads, check whether it applies per file or to all files together.
1,000 or 1,024 bytes?
Portals count a kilobyte either way. PixKB keeps the file at or under 100,000 bytes, so it passes a 100 KB limit whichever way the portal counts.
Frequently asked questions
Can a scanned PDF really fit in 100 KB?
One or two pages, yes: our 6.34 MB two-page scan came out at 96 KB and readable. Our 10-page scan couldn't get below 276 KB with readable pages.
Will my form's text and fields survive?
Yes. Only the photos and scans inside are recompressed; text, fonts, links and form fields are copied unchanged.
What does Rebuild pages as images do?
It turns each page into a compressed picture to reach the limit. Pages look the same, but text can't be selected or searched and form fields become flat. It's offered only when it would actually help.
Why is my PDF still over 100 KB?
Too many pages for the limit, or images in print colours (CMYK), which PixKB doesn't recompress to avoid changing how they look. The message tells you which.
My PDF is already under 100 KB. What happens?
You get your original file back unchanged.
Should I make the PDF greyscale?
Only if the paper itself is colourful: our colourful certificate was 17% smaller in greyscale; plain black-on-white pages hardly changed.
Is my document uploaded?
No. The PDF is compressed in your browser and saved to your device. It also works offline after your first compression, or after you tap Make this tool available offline.
Is there a watermark?
No watermark, no signup and no daily limit.