PDF Compressor
Reduce PDF file size by removing unused objects and optimizing structure — no image re-encoding, no quality loss. No upload, no sign-up.
Your files never leave your device. All processing happens in your browser.
How PDF Optimization Works
PDFs are structured as a collection of objects — fonts, images, pages, metadata, and cross-reference tables. When PDFs are edited or exported from productivity software, they often accumulate:
- Dead objects — resources that were added and later removed but never cleaned up
- Duplicate font subsets — the same font embedded multiple times with slightly different names
- Uncompressed cross-reference tables — the index that maps object numbers to file offsets
- Redundant metadata — creation/modification timestamps, software version strings, and preview thumbnails
This tool re-saves the PDF using pdf-lib with object stream compression enabled, which packs the cross-reference data into compressed streams and removes the dead objects in the same pass.
When This Tool Helps Most
| PDF source | Typical savings | Reason |
|---|---|---|
| Microsoft Word / Excel / PowerPoint | 10–40% | Unused font glyphs, uncompressed XRef |
| Google Docs export | 5–20% | Metadata overhead, duplicate resources |
| macOS Pages / Numbers | 5–15% | Preview thumbnails, redundant metadata |
| Adobe Acrobat (annotated) | 2–10% | Annotation history objects |
| Scanned documents (image PDF) | 1–5% | Size dominated by embedded images |
| Already-optimized Acrobat PDF | 0% | Object streams already enabled |
Frequently Asked Questions
How much smaller will my PDF get?
It depends on how the PDF was created. PDFs exported from Microsoft Word, Google Docs, or macOS Pages often shrink 10–40% because those apps leave unused font glyphs, duplicate resources, and redundant metadata. Scanned PDFs (where size is dominated by embedded images) typically see only 1–5% reduction, because this tool optimizes structure rather than re-encoding images.
Why is there no quality slider like image compression tools?
PDF "quality" is mostly about embedded images. This tool uses pdf-lib, which can read and restructure PDF objects but cannot re-encode JPEG images inside the file. A quality slider would imply image re-encoding that does not actually happen here. What the tool does — cross-reference compression and unused object removal — is the most reliable improvement available without re-encoding.
Will the compressed PDF look different?
No. The optimization removes structural overhead only — redundant object copies, unused resources, and padding. Text, images, fonts, and layout are preserved exactly.
Are my files uploaded to a server?
No. The entire process runs in your browser using the pdf-lib JavaScript library. Your files never leave your device.
My PDF did not get smaller. Why?
The tool reports "Already optimized" when the re-saved file is not smaller than the original. This happens when the PDF was already created with object stream compression enabled — common for PDFs from Adobe Acrobat, Chrome, or recent versions of macOS Preview.
Related Tools
- PDF Merger →
- PDF Splitter → Extract pages to reduce size another way.
- Compress images for email → If your PDF is large due to images, compress the source images first.
- Browse all tools →