How browser-based PDF compression works
This tool uses pdf.js to render each page of your PDF to a canvas at your chosen DPI, then JPEG-encodes that canvas at the chosen quality, and finally rebuilds a fresh PDF from those JPEG images using pdf-lib. The output is consistently smaller than the original — the compression ratio depends on your input.
Trade-off: text becomes images. The output PDF won't be searchable / selectable. For most use cases (screen viewing, emailing, sharing on WhatsApp / Slack), that's acceptable. For text-preserving compression, you'd need server-side tools like Ghostscript that re-encode internal streams without rasterizing.
FAQs
How much does it compress?▼
Depends on the PDF. Image-heavy PDFs (scans, presentations) often compress to 20-50% of their original size at the medium preset. Text-only PDFs (already efficiently encoded) typically see 60-90% retention. Use the Maximum preset to reduce file size aggressively at the cost of resolution.
Why does my text become an image after compression?▼
This tool rasterizes each page to an image at the chosen DPI, then rebuilds the PDF from those images. That's how it achieves consistent compression across any PDF format. Text is no longer selectable / searchable in the output. For text-preserving compression, use a server-side tool like Ghostscript (not available in-browser).
What DPI should I pick?▼
150 DPI is good for printing. 110 DPI is fine for laptop / phone reading. 72 DPI is ideal for emailing or web — file sizes are smallest. If your input PDF is a high-resolution scan, dropping from 300+ DPI to 110 DPI will dramatically reduce size with barely-visible quality loss on screen.
Are uploads private?▼
Nothing is uploaded. The file is processed entirely in your browser using pdf.js + pdf-lib. Verifiable in DevTools → Network tab during compression: zero outbound requests for the file.
What's the file size limit?▼
There's no fixed cap — it depends on your device's available memory. Browser-side rasterization is RAM-intensive; ~100 page PDFs work on most laptops. For 500+ page PDFs, expect slow processing or use a server-based tool.