How PDF Compression Works
Our Compress PDF tool reduces file size using two techniques applied entirely inside your browser:
- Object-stream packing: Modern PDFs store their internal objects (fonts, metadata, annotations) separately. We repack these into compact object streams, which can shave a meaningful percentage off any PDF's size with zero quality loss.
- JPEG image recompression: For PDFs containing photos or scanned pages, the images are the biggest contributors to file size. Our tool scans the PDF for embedded JPEG images and re-encodes them at your chosen quality level using your browser's native Canvas API. This is the same technique used by professional tools.
Which Setting Should I Choose?
- Maximum compression (20–30%): Best for scanned documents you need to email or upload to a portal. Noticeable quality loss on photos, but text stays readable.
- High (40–50%): Good all-rounder for mixed documents.
- Medium (60–70%): Recommended for most use cases. Significant size reduction with barely noticeable quality change.
- Low (80–90%): Almost lossless. Minimal size savings, best for archiving documents where image fidelity matters.
Your Files Stay Private
Every step of the compression process runs locally in your browser tab using PDF-lib and the HTML5 Canvas API. Your PDFs are never uploaded to any server.