Why is the size reduction sometimes small?

PDF compression results depend heavily on the original file. PDFs already produced by modern software (like newer versions of Adobe Acrobat or Microsoft Office) are often already well-compressed. Scanned PDFs with large embedded images see minimal reduction without re-encoding the images (which requires server-side processing or ImageMagick). This tool focuses on structural PDF-level optimisations that are safe and lossless.

Are my files uploaded to a server?

No — your PDF files never leave your device. The entire compression process uses pdf-lib, an open-source JavaScript library that runs client-side in your browser. No data is sent anywhere.

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Compress PDF

Reduce PDF file size instantly in your browser — using DEFLATE stream compression, duplicate object removal, metadata pruning and object-stream compaction. Single file or batch mode. No uploads, no server, no watermarks.

✓ DEFLATE Stream Compression ✓ Duplicate Object Removal ✓ Metadata Pruning ✓ Batch Mode ✓ Lossless ✓ No Server Upload

PDF Compressor

Single file or batch — all processing runs in-browser using pdf-lib

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Drop a PDF here

or click to select file

Select PDF

Processed in-browser · File never uploaded to any server

🔒 Powered by pdf-lib open-source library · Files never leave your browser · No API, no server

How PDF Compression Works

Lossless structural optimisations applied by pdf-lib

⚡ DEFLATE Encoding 🔁 Deduplication ✂️ Metadata Pruning 📦 Object Streams 🗂️ XRef Optimisation

Parse PDF

pdf-lib parses the full PDF object graph — pages, fonts, images, streams, cross-reference table.

Compress Streams

All content streams are (re-)compressed with DEFLATE — the most effective lossless stream filter in the PDF spec.

Remove Redundancy

Unused objects, duplicate indirect references and vestigial metadata are pruned before serialisation.

Compact XRef

The cross-reference table is written as a compressed object stream (PDF 1.5+) for further size savings.

Frequently Asked Questions

How does the PDF compressor work?

The tool uses pdf-lib to parse your PDF and rewrite it with structural optimisations: all content streams are compressed with DEFLATE encoding, duplicate objects are removed, metadata is pruned, and the cross-reference table is written as a compressed object stream. This runs entirely in your browser — no file is sent to any server.

Is the compression lossless?

Yes — completely lossless. This tool compresses data streams and removes redundant objects but does not re-encode, downsample or modify any images, fonts, or page content. The visual appearance of your PDF is identical before and after compression.

Why is the reduction small for some PDFs?

Results depend on the source PDF. PDFs created by modern software are often already well-compressed structurally, leaving little room for further reduction. Scanned PDFs with large embedded JPEG images see minimal reduction because JPEG re-compression (which would be lossy) is beyond the scope of structural PDF compression.

Can I compress multiple PDFs at once?

Yes — switch to Batch Mode using the toggle at the top of the tool. Add multiple PDFs, then click Compress All. Each file is compressed independently and you can download them all at once as a ZIP archive.

About ToollLive Free PDF Compressor

ToollLive's free PDF compressor is the easiest way to reduce PDF file size online without any sign-up. Upload a PDF and the tool applies multiple lossless optimisations using the open-source pdf-lib library — DEFLATE stream compression, duplicate object removal, metadata pruning and compressed cross-reference table rewriting. This PDF size reducer works entirely in your browser so your files never leave your device. Use batch mode to compress multiple PDFs at once and download them all as a ZIP. The compression is completely lossless — the PDF quality is preserved perfectly while the file size decreases. Whether you need to shrink PDF for email, upload limits or storage, this free tool handles it instantly. Also try Combine PDFs, Rearrange PDF Pages and PDF to Excel.