PDF Compress
Optimize PDF internal structure to reduce file size.
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About PDF Compress
PDF Compress reduces the file size of your PDF documents, making them easier to email, upload, or share. Compression works by optimizing internal streams with no visible quality loss for most documents.
How to Compress a PDF
- 1Upload the PDF you want to compress.
- 2Select a compression level: standard or maximum.
- 3Click Compress and wait for processing to complete.
- 4Download the compressed PDF and compare the file sizes.
Popular Use Cases
Fit email attachment limits
Shrink reports or scanned files that exceed the 10–25 MB attachment cap enforced by most email providers.
Upload to application portals
Government, university, and job portals often enforce strict size limits. Compress your PDF to fit without re-scanning anything.
Share faster in messengers
Smaller files send faster on Slack, WhatsApp, or KakaoTalk and use less mobile data on the receiving end.
Save cloud storage space
Compress archived documents so more of them fit in the free tiers of Google Drive, Dropbox, or OneDrive.
Why FileZoom
No upload — files stay private
Compression runs fully in your browser. Sensitive contracts and statements are never transmitted to a server.
Free with no limits
Compress as many PDFs as you need — no account, no watermarks, no daily quota.
Two compression levels
Standard mode preserves maximum fidelity; maximum mode squeezes out every last kilobyte when size matters most.
Instant size comparison
See the original and compressed sizes side by side before downloading, so you know exactly how much you saved.
Formats & Features
| Supported input | Any PDF — works best on image-heavy or scanned documents. |
|---|---|
| Output | A compressed PDF with the same pages and layout, optimized for a smaller file size. |
| Compression levels | Standard (minimal quality impact) and Maximum (smallest size, with light image resampling). |
| Typical reduction | 50–80% for image-rich PDFs; smaller gains for text-only files. |
| Text & search | Preserved. Text stays selectable and searchable after compression. |
| Processing | 100% in your browser with pdf-lib. Files are never uploaded. |
How It Works
FileZoom rebuilds your PDF's internal structure with pdf-lib, running as JavaScript in your browser. Redundant objects are removed, content streams are re-encoded with stronger compression, and at maximum level embedded images are resampled to a more efficient resolution. All of this happens in your device's memory — the document never travels over the network, which is also why compression starts instantly with no upload progress bar.
Tips & Best Practices
- Try Standard first — it often hits your size target with no visible quality change. Switch to Maximum only if needed.
- Scanned PDFs (photos of pages) shrink the most. Pure-text PDFs are already small and compress little.
- Compressing twice rarely helps — the first pass removes nearly all the recoverable size.
- Need a specific size for an upload? Compare the before/after sizes shown and re-run at Maximum if you're still over.
FAQ
How much smaller will my PDF get?
Results vary by content. PDFs with many images can be reduced by 50-80%. Text-only PDFs may see smaller reductions.
Will compression reduce image quality?
Standard compression optimizes file structure with minimal quality impact. Maximum compression may reduce image resolution slightly.
Is compression done on a server?
No. All compression happens locally in your browser using pdf-lib. Your files are never uploaded.
Can I compress a PDF multiple times?
You can, but successive compressions yield diminishing returns. The first pass typically achieves the greatest reduction.
Is there a maximum file size I can compress?
No hard cap is enforced. Files of several hundred megabytes work; the practical limit is your device's memory.
Will text stay selectable and searchable?
Yes. Compression changes how the file is stored, not its content — text layers, fonts, and search all keep working.
Why did my PDF barely shrink?
If a PDF is mostly text or was already optimized, there is little left to remove. Image-heavy and scanned PDFs see the biggest reductions.
Is the compressed PDF safe to print?
Yes. Page dimensions and layout are unchanged, so printed output matches the original.