How does PDF compression work?

This tool re-saves your PDF using object stream compression (deflate encoding) and removes embedded metadata, reducing structural overhead.

Why didn't my PDF get smaller?

PDFs that are primarily large images (scanned documents) won't compress much — the image data is already compressed. Image-level recompression requires a server-side tool.

Will the compressed PDF look different?

No. Compression only affects the file structure, not the visible content. Fonts, text, and images are preserved exactly.

Is my PDF uploaded to a server?

No. All processing happens locally in your browser using pdf-lib. Your file never leaves your device.

Compress PDF

Reduce PDF file size online — free, instant, browser-based.

🗜️

Drop your PDF here or click to upload

Only .pdf files accepted → Outputs smaller .pdf

About Compress PDF

Free online PDF compressor. Reduce your PDF file size by removing redundant metadata and re-encoding the PDF structure. Works entirely in your browser — your files are never uploaded to any server.

How to Use Compress PDF

Upload your PDF by clicking the upload area or dragging and dropping.
Click 'Compress PDF' to start the optimisation process.
The compressed PDF downloads automatically when done.
Review the size comparison to see how much space was saved.

Frequently Asked Questions

How does PDF compression work?: This tool re-saves your PDF using object stream compression (deflate encoding) and removes embedded metadata, reducing structural overhead.
Why didn't my PDF get smaller?: PDFs that are primarily large images (scanned documents) won't compress much — the image data is already compressed. Image-level recompression requires a server-side tool.
Will the compressed PDF look different?: No. Compression only affects the file structure, not the visible content. Fonts, text, and images are preserved exactly.
Is my PDF uploaded to a server?: No. All processing happens locally in your browser using pdf-lib. Your file never leaves your device.