Compress PDF
Reduce PDF file size online for free. Optimise PDFs for email and web sharing.
Drop a PDF to compress
.PDF, APPLICATION/PDF supported
About this tool
Large PDF files can be slow to email, upload, or share. This PDF compressor reduces file size by re-encoding the PDF structure using object stream compression — a technique that packs PDF objects more efficiently without removing content. It works especially well on PDFs generated by tools that do not apply stream compression (common in older software, export tools, and scanned documents).
- ✅ Free to use, no sign-up required
- ✅ Files never leave your device
- ✅ Instant conversion
- ✅ Works on any browser and device
How it works
The tool uses pdf-lib to re-save the PDF with the useObjectStreams option enabled, which compresses the internal object streams using deflate compression. This does not downsample images or remove content — it optimizes the structural encoding of the PDF. The tool displays the original and compressed file sizes so you can see the reduction.