How much can I reduce a PDF's size?

Depending on the content, PDF compression can reduce file size by 30-70%. PDFs with large images see the most reduction.

Will compression reduce the visual quality?

Our tool uses lossless object stream optimization where possible. For image-heavy PDFs, compression is applied intelligently to balance quality and size.

100%. All compression happens locally in your browser using pdf-lib. Your documents are never uploaded to any server.

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PDF Compressor — Bulk Size Reducer

Q: Can I compress multiple PDFs at once?

Yes! CosmoxHub supports bulk PDF compression. Upload multiple files and they will be processed in parallel, with a ZIP download at the end.

New

Compress single or multiple PDFs instantly. Reduce file size without quality loss. 100% private — no server uploads.

Compression Settings

Compression Level

Drop PDFs to Compress

Drag & drop one or multiple PDF files. Processed instantly in your browser — zero server uploads.

PDF Compressor — Usage Guide

Upload PDFs

Select one or multiple PDF files. Drag & drop supported for bulk uploads.

Choose Level

Low keeps max quality with light compression. Medium is balanced. High gives smallest file size.

Compress All

All files are processed in parallel — no waiting for one to finish before next starts.

Download

Save files individually or use Download All to get everything at once.

Frequently Asked Questions

Will quality be affected?

Low and Medium levels retain near-identical visual quality. High removes redundant metadata and optimizes streams while keeping the content readable.

Can I compress multiple PDFs at once?

Yes! Add as many PDFs as you want. All are compressed simultaneously in parallel for maximum speed.

Is it private?

100%. Everything runs in your browser using pdf-lib. Your files never leave your device.

What is the maximum file size?

There is no enforced limit. Large files may take a few seconds depending on your device speed.

Need to compress PDF files on mobile or desktopwithout risking your document's privacy? CosmoxHub offers the market's only fully localized, edge-computing PDF Size Reducer. Unlike other free tools that upload your sensitive data to cloud servers, our compressor processes your files directly within your browser utilizing advanced WebAssembly.

Whether you need to bypass a 5MB email attachment limit or upload a lightweight portfolio to a job portal, CosmoxHub strips out redundant metadata and optimizes data streams while preserving crisp text and sharp image fidelity. Stop paying for expensive desktop software—reduce your PDF size securely, instantly, and 100% free.

Verified Tool QualityLive & Secure

This tool has been extensively tested for accuracy and performance. On April 2026, our engineers verified the core logic to ensure 100% reliability and precision. Like all CosmoxHub utilities, this tool runs entirely in your browser. No data is ever sent to a server.

No Uploads

No Logs

HIPAA & GDPR Ready

Open Source Logic

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