PDF Compressor
Compress PDF files directly in your browser. No uploads, no signup. Your files never leave your device.
What this tool actually does
This compressor performs lossless structural compression using the open-source pdf-lib library. It rewrites your PDF from scratch: redundant and unused objects are dropped, the internal structure is repacked into compact object streams, and editing metadata (title, author, subject, keywords) is stripped out. Because no image is ever re-encoded, the visual quality of every page is byte-for-byte identical to the original — text stays sharp at any zoom level.
A worked example
A typical 60-page report exported from Word carries a lot of structural baggage: incremental-save leftovers, duplicated font descriptors, and editing metadata. Run through this tool it looks like this (sizes formatted by the tool's own code):
Original
3.99 MB
Compressed
2.86 MB
Saved
28.3%
Your mileage will vary — that's the honest truth of structural compression. Files that were edited and re-saved many times, exported from office software, or filled with form data tend to shrink the most. A PDF that is essentially a container for photos or scans will barely change, because the images themselves are left untouched.
Choosing a compression level
Low rewrites the file without object streams, which keeps maximum compatibility with very old PDF readers. Medium and High enable object-stream packing — the strongest lossless restructuring pdf-lib offers — and currently produce equivalent output. If your PDF only ever opens in modern software (browsers, Acrobat, Preview), use Medium or High.
How to use PDF Compressor
- 1Drop or select a PDF file from your device.
- 2Choose a compression level: Low, Medium, or High.
- 3Click 'Compress PDF' and wait for the result.
- 4Download your compressed PDF.
Frequently Asked Questions
Is my PDF uploaded anywhere?
No. The PDF is processed entirely in your browser using pdf-lib. You can watch the network tab in your browser's developer tools while compressing — no file data is transmitted.
Why is my output similar in size?
Structural compression can't shrink what dominates image-heavy files: the embedded images themselves. Scanned documents and photo albums compress little; text documents and office exports compress well.
Will text or image quality change?
No. This tool never re-encodes page content, so text and images render identically to the original — only the file's internal structure is repacked.
Is there a file size limit?
Only your device's available memory. Very large files (hundreds of MB) may be slow or fail on low-memory devices.
Does it work on mobile?
Yes. The tool is fully responsive and works in mobile browsers, though large files compress faster on a laptop.
Limitations & Privacy
- Embedded images are not downsampled or re-encoded, so scans and photo-heavy PDFs may shrink only a few percent. For those files, desktop tools that re-encode images will do better.
- Document metadata (Title, Author, Subject, Keywords) is cleared as part of compression. Keep your original if you need those fields.
- Password-protected or encrypted PDFs cannot be processed — decrypt them first.
- Processing happens in your browser's memory, so the practical size limit depends on your device.
- Privacy: your PDF never leaves your device. It is loaded, rewritten, and saved entirely locally by pdf-lib.