Compress PDF
Reduce PDF file size by removing unused objects and re-encoding images. Runs entirely in your browser.
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Why Use This Tool?
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📉 Expected Results
- • Text-heavy PDFs: 10–30% smaller
- • Photo-heavy PDFs: 40–70% smaller
- • Already-compressed PDFs: minimal change
- • Scanned document PDFs: limited reduction
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How Browser-Based PDF Compression Works
PDFs accumulate unused objects over time — deleted text, replaced images, redundant cross-references. This tool uses pdf-lib to rebuild the PDF from scratch, discarding those unused objects. At medium and high compression levels it also re-encodes embedded JPEG images at lower quality using the browser's Canvas API, which is the primary driver of size reduction for photo-heavy documents.
How to Compress a PDF
- Upload your PDF by clicking the upload area or dragging and dropping.
- Choose a compression level — Medium is the recommended starting point.
- Click Compress PDF and wait for processing.
- Review the size savings shown in the result panel.
- If savings are small, try High compression.
- Download the compressed file.
Limitations
Browser-based compression has some constraints compared to server-side tools. PDFs that consist entirely of vector graphics or pre-compressed JPEG images near maximum compression will see minimal gains. Password-protected PDFs cannot be processed. For maximum compression of production documents, a server-side tool like Ghostscript can achieve better results by downsampling images beyond what the Canvas API supports.
Frequently Asked Questions
How much can I expect to reduce the file size?
Results vary. PDFs that are mostly text may shrink by 10–30% from object-stream optimisation alone. PDFs with high-resolution photos can shrink by 50–70% at high compression. Scanned documents and PDFs already compressed at the source may show little change.
Is my PDF uploaded to a server?
No. All compression happens in your browser using pdf-lib. Your file never leaves your device.
Will compression damage my PDF?
No pages, text, or structure are removed. At high compression, embedded images will have reduced quality — visible as slight blurriness on photos. Text, vector graphics, and document structure are unaffected.
Related Tools
Merge PDF — combine several PDFs, then compress the result. PDF to JPG — extract pages as images. Image Optimizer — compress images before converting them to PDF.