Compress PDF Files Online
Reduce PDF file sizes while keeping your documents looking great. Perfect for email attachments, web uploads, and archiving.
Drop a PDF file here or click to browse
Up to 100 MB
Optimize PDF structure and metadata
Three compression levels to choose from
100% client-side — files never leave your device
No file size limits for compression
Instant download of compressed files
No watermarks, no sign-up required
Understanding PDF Compression
PDF (Portable Document Format) files can grow large due to embedded images, fonts, metadata, and redundant objects. Effective PDF compression targets each of these areas to reduce file size while preserving document fidelity.
How PDF Compression Works
Compresso's PDF compressor uses several techniques: object deduplication (removing redundant copies of fonts and images), stream recompression (applying more efficient encoding to content streams), image recompression (re-encoding embedded images at optimized quality), and metadata cleanup (stripping unnecessary editing history and producer information).
When to Compress PDFs
- Email attachments — many email providers limit attachments to 10-25MB
- Web uploads — smaller PDFs mean faster downloads for users
- Document management — save storage space on scanned documents
- Form submissions — many portals have file size limits
Privacy-First PDF Compression
PDFs frequently contain sensitive data — contracts, financial statements, medical records, legal documents. Unlike iLovePDF, SmallPDF, and Adobe Acrobat online, Compresso never uploads your PDFs to any server. All processing happens in your browser using the pdf-lib library. Your documents stay on your device, period.
Related Tools
- Compress JPG — for image files
- Compress PNG — for graphics and screenshots
- Compress DOCX — for Word documents
- Compress PPTX — for PowerPoint presentations
- Compress for Email — optimize any file for email
Frequently Asked Questions
How much can I reduce my PDF file size?
Compression results depend on your PDF's content. Documents with embedded images typically compress 30–60%, while text-heavy PDFs may see 10–30% reduction. Scanned documents often achieve the best results.
What's the difference between compression levels?
Low compression preserves maximum quality with minimal size reduction. Medium offers a balanced trade-off. High compression provides maximum size reduction but may slightly affect embedded image quality.
Will compression affect my PDF's quality?
Compression primarily optimizes file structure, removes duplicate objects, and recompresses embedded images. Low and medium compression maintain original quality, while high compression may cause minimal quality reduction in embedded images.
Is it safe to compress PDFs with Compresso?
Absolutely. Compresso processes everything in your browser — your files are never uploaded to any server. This is critical for PDFs containing contracts, financial data, medical records, or other sensitive information.
Can I compress password-protected PDFs?
Password-protected PDFs are not currently supported. Please remove the password first, then compress.
How does Compresso compare to Adobe Acrobat for PDF compression?
Adobe Acrobat offers more advanced PDF editing features, but requires a paid subscription and uploads files to Adobe's cloud. Compresso is free, instant, and keeps your documents completely private.
Does PDF compression remove annotations or form fields?
No. Compresso preserves all PDF content including text, annotations, form fields, and bookmarks. Compression targets file structure optimization and embedded image recompression.
Can I compress multiple PDFs at once?
Currently Compresso processes one PDF at a time for the best results. Upload your next PDF as soon as the first one is done.
Last updated: March 2026