PDF Compressor
Reduce PDF file size online. Processed in browser.
Drag & drop your PDF here
or click to browse
Supports PDF files
Your PDF is processed in your browser. It is not uploaded to any server.
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How to use PDF Compressor
1
Drag and drop a PDF file or click to browse. The tool will show the file size and page count.
2
Select a compression level: Low (minimal), Medium (strip metadata + re-save), or High (maximum optimization).
3
Click "Compress PDF" to process. The tool will compare the compressed size with the original.
4
If compression was successful, download the smaller PDF. If the PDF is already optimized, the original is preserved.
How it works
This PDF compressor processes files entirely in your browser using the pdf-lib library:
- Loading: The PDF file is read into memory using the FileReader API and parsed by pdf-lib.
- Low compression: The PDF is re-serialized with object streams enabled, which can consolidate redundant data structures and reduce file size.
- Medium compression: In addition to re-serialization, all metadata (title, author, subject, keywords, creator, producer, dates) is stripped from the PDF.
- High compression: Applies all medium-level optimizations plus attempts additional reduction strategies. Note that browser-based tools have inherent limitations compared to desktop PDF software.
- Size check: After compression, the actual byte size of the result is compared with the original. If the compressed version is not smaller, the original file is kept and you are notified.
- Privacy: Your PDF never leaves your device. All processing is done locally using JavaScript. No data is uploaded to any server.
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Frequently Asked Questions
Is my PDF uploaded to a server?
No. Your PDF is processed entirely in your browser using JavaScript. It is never uploaded, transmitted, or stored on any server. Your privacy is fully protected.
Why didn't my PDF get smaller?
Browser-based PDF compression has limitations. If the PDF is already well-optimized, uses efficient encoding, or contains content (like embedded fonts or complex vector graphics) that cannot be compressed further by re-serialization, the file size may not decrease. In this case, the tool will keep the original and let you know.
Can it compress image-heavy PDFs?
Browser-based compression has limited ability to recompress embedded images. For PDFs that are mostly images, the reduction may be small. For better results with image-heavy PDFs, consider extracting the images and using our Image Compressor tool to compress them individually before creating a new PDF.
Does it work with password-protected PDFs?
The tool attempts to process password-protected PDFs, but some encryption methods are not supported in the browser. If the tool cannot read your PDF, you will see an error message. Please remove password protection before compressing.
What compression levels are available?
Low: Re-saves the PDF with object streams, which can remove redundant internal structures. Medium: Additionally strips all metadata (title, author, creation date, etc.). High: Applies all medium optimizations plus additional strategies. For most PDFs, Medium offers the best balance of compression and reliability.
Is there a file size limit?
There is no hard limit, but very large PDFs (100MB+) may be slow to process or may exceed browser memory limits. Performance depends on your device and browser.