How to compress a PDF
- Drop a PDF into the box above (one file at a time, max 100 MB).
- Click Compress PDF.
- The compressed file downloads automatically. The before/after sizes are shown so you can see how much was saved.
Why the savings are modest
Real PDF compression generally means re-encoding the embedded JPEG and PNG images at lower quality, downsampling them, or replacing fonts. Doing that well requires tools like Ghostscript, Pdfium, or commercial libraries — none of which run in a web browser. Browser-side compression instead repacks the PDF using object streams, drops unused indirect objects, and removes redundant metadata. That helps, but it is not magic.
If your PDF is mostly scanned images and you need to email it under a 10 MB cap, consider a desktop converter or print-to-PDF at lower resolution.
Privacy
Compression runs entirely inside your browser. The original PDF is never uploaded. You can verify this by checking your browser's network panel.
FAQ
Why did my file get bigger? Object stream packing can occasionally produce a slightly larger file when the source PDF used a more compact stream layout that pdf-lib doesn't replicate.
Will form fields and signatures survive? Form fields stay intact. Digital signatures will be invalidated because saving the PDF changes the byte content.
Is the visual quality affected? No. Browser compression does not touch image data.