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Quick answer
To compress a PDF to 100KB, open Compress PDF, add your file, choose Extreme (80–90% smaller) and click Compress PDF. The new size is shown before you download. One or two scanned pages usually fit under 100KB on Extreme, and text-only PDFs often do on Moderate.
How to compress a PDF to 100KB in 3 steps
Add your PDF
Open Compress PDF and drop in your file. PDFs up to 200 MB work, including scans.
Choose Extreme
Extreme is the best starting point for a 100KB target. The tool shows the original and compressed sizes, so you can check the result straight away.
Check the size and download
If the new size is under 100KB, download it. If not, see the fixes below.
What fits in 100KB
Text barely adds to a PDF's size. Scanned pages and photos are what make it heavy. As a rough guide:
Swipe to compare →
| Your PDF | Level to try | Under 100KB? |
|---|---|---|
| Text-only document, several pages | Moderate | Usually |
| 1 scanned page | Extreme | Usually |
| 2 scanned pages | Extreme | Sometimes |
| 3 or more scanned pages or photos | Extreme, then trim pages | Rarely |
If your PDF is still over 100KB
- Try the next level up, up to Extreme.
- Remove blank or unneeded pages with Delete PDF pages, then compress again.
- If it is a scan, re-scan at 150 DPI in grayscale. It makes a much smaller file to begin with.
- Still too big? Split the PDF into two files and upload each one if the form allows it.
Scan settings that land under 100KB
The easiest way to hit 100KB is to create a smaller file from the start. If you are scanning a document for a 100KB limit:
- Resolution: 150 DPI is plenty for reading and printing. 600 DPI makes files several times bigger for no visible gain.
- Color: grayscale.
- Pages: one page per file where the form allows it.
- Phone scans: use the Notes app on iPhone (Scan Documents) or Google Drive on Android, which crop and flatten pages automatically.
How to check a PDF's size in KB
- iPhone: in the Files app, touch and hold the PDF and tap Get Info.
- Android: in Files by Google, tap the three dots next to the file and choose File info.
- Mac: select the file in Finder and press Command-I.
- Windows: right-click the file and choose Properties, or switch File Explorer to Details view.
Compress PDF also shows the original and compressed sizes on screen, so you can check before you download.
Where you'll run into a 100KB limit
- Online forms that ask for a signed page or a single ID scan.
- School and scholarship portals with a strict per-file limit.
- Older government and employer systems built around small uploads.
- Signature pages sent back separately from a contract.
Frequently asked questions
How do I compress a PDF to 100KB for free?
Open Zappy Compress PDF, add your file, choose Extreme and click Compress PDF. The new size is shown before you download, so you can confirm it is under 100KB.
Can every PDF be compressed to 100KB?
Not always. Long scanned documents may not fit in 100KB even on Extreme. Remove pages you don't need or split the file into parts.
Will the text still be readable?
Yes. Compression shrinks images and scans, not text, so typed words stay sharp at every level.
Can I compress a PDF to 100KB on my phone?
Yes. Open Compress PDF in Safari or Chrome, choose Extreme and check the size shown before you download.
How many pages fit in 100KB?
Usually one or two scanned pages on Extreme, or many more pages if the PDF is typed text rather than scans.
Does it work on iPhone and Android?
Yes. Open Compress PDF in Safari or Chrome and choose the file from Files or your Downloads.
What happens to my file?
It is compressed on our server and deleted automatically afterwards. It is never shared.