Free PDF Compressor
Reduce your PDF file size using FlateDecode zlib compression — entirely in your browser. No server upload, no quality loss, instant results. Free forever.
Drop a PDF here or click to upload
PDF files only · Processed entirely in your browser
How it works
- Compression runs entirely in your browser using the pdf-lib library — your file is never uploaded.
- Re-encodes all object streams with FlateDecode (zlib) compression and removes redundant data.
- Best results on PDFs that weren't previously optimised. Image-heavy PDFs may see smaller reductions.
Why Compress PDFs?
PDF files exported from design tools (Adobe InDesign, Illustrator, PowerPoint) often contain redundant metadata, uncompressed object streams, and embedded fonts that inflate file size significantly. A 50-page report exported from PowerPoint can easily reach 20–40MB when it could be 3–8MB with proper compression.
For email attachments, most email providers impose limits between 10MB and 25MB. Gmail's limit is 25MB as an attachment (or 50MB received). Outlook defaults to 20MB. Reducing PDF size ensures your documents reach their recipients without being rejected.
For web publishing — embedded PDF viewers, downloadable whitepapers, and ebooks — smaller PDFs improve perceived performance significantly. A 2MB PDF downloads 5× faster than a 10MB PDF on an average mobile connection.
20–50%
Typical size reduction for text-heavy PDFs
25MB
Gmail attachment limit
100%
Lossless — no quality degradation
Frequently Asked Questions
Everything about PDF compression and how it works.
How does PDF compression work?
The tool re-encodes all PDF object streams with FlateDecode (zlib) compression and removes redundant data. This is lossless — text, vectors, and image quality are preserved perfectly.
How much will my PDF be compressed?
Text-heavy PDFs typically see 20–50% reduction. PDFs with already-compressed images may show minimal reduction (shown as 'Already optimal').
Is this PDF compression lossless?
Yes. No images are downsampled or degraded. Only the PDF structure is re-encoded more efficiently.
Will this work on password-protected PDFs?
No. Encrypted PDFs need to be unlocked before compressing. Use our PDF Locker after compression to re-add a password if needed.
Is my PDF uploaded to a server?
No. Processing is entirely browser-based using pdf-lib. Your PDF never leaves your device — safe for confidential documents.
Why is reducing PDF size important?
Large PDFs are slow to email (many providers cap at 10–25MB), slow to upload, and consume storage. Smaller PDFs load faster in browsers and PDF viewers.