Reduce PDF file size online — free, fast, and completely private. This browser-based PDF compressor shrinks your documents by recompressing embedded images and repacking internal PDF objects. No files are uploaded to any server. Everything runs directly in your browser, so your documents stay on your device at all times.
How Our PDF Compressor Reduces File Size
Large PDFs are usually caused by embedded images — scanned pages, photos, and graphics. This tool uses two techniques to reduce file size without rebuilding the document from scratch:
- JPEG image recompression: Embedded JPEG images are re-encoded at your chosen quality level using your browser's native Canvas API. This is typically where the biggest size savings come from in image-heavy or scanned PDFs.
- Object-stream packing: PDF files store internal objects such as fonts, metadata, and annotations separately. Repacking these into compact object streams reduces overhead with zero quality loss.
If you need to reduce file size further by removing unnecessary pages, you can also use our Remove Pages tool.
Which Compression Setting Should I Choose
- Maximum (20–30% quality): Best for scanned documents you need to email or upload to a portal. Noticeable quality reduction on photos, but text stays readable.
- High (40–50%): A good all-rounder for mixed documents with both text and images.
- Medium (60–70%): Recommended for most use cases. Significant size reduction with barely noticeable quality change.
- Low (80–90%): Near-lossless compression. Minimal size savings — best for archiving documents where image quality matters.
Private Browser-Based PDF Compression
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 — making this tool safe to use with confidential or sensitive documents.