A 20 MB PDF will bounce off most email servers, fill up cloud storage quotas, and frustrate mobile users waiting for it to load. Browser-based PDF compression can reduce file size by 60–85% in seconds — without installing anything or uploading your document to a third-party server.
How browser-based PDF compression works
This tool uses PDF.js to render each page of your PDF onto an HTML canvas element. Each rendered canvas is then exported as a JPEG image at your chosen quality. Those JPEG images are reassembled into a new PDF using pdf-lib. The result is smaller because JPEG compression removes fine detail that is imperceptible at screen resolution.
The key trade-off: because pages become JPEG images, text will no longer be selectable or searchable in the output PDF. This method is best for scanned documents, image-heavy reports, and presentation exports — not for PDFs where you need to copy text or use Ctrl+F.
Choosing a compression level
Three levels are available, each trading file size for visual sharpness:
- Low Compression (20–40% smaller) — renders at 1.8× scale with 88% JPEG quality. Preserves near-original visual quality. Best for presentations and design files where appearance matters.
- Recommended (40–70% smaller) — renders at 1.2× scale with 72% JPEG quality. Balanced starting point for most use cases. Good enough for email attachments and shared reports.
- Maximum (60–85% smaller) — renders at 0.75× scale with 52% JPEG quality. Smallest possible output. Fine for archiving low-priority documents or meeting strict size limits, at the cost of reduced sharpness.
Start with Recommended. Only switch to Maximum if the file is still too large, and use Low only when visual quality is the top priority.
When will compression make the file larger?
Text-only or vector-heavy PDFs (like a spreadsheet export or a simple contract) can actually grow larger after compression. The original PDF stores text as compact text encoding — when re-rendered as JPEG images, even blank white areas take up JPEG data. If your compressed output is larger than the original, the original was already well-optimised and this approach is not the right tool for it.
File size limits and performance
The maximum file size is 100 MB. For large PDFs (50+ pages), compression runs page by page in the browser, so it may take 30–90 seconds depending on your device. The progress bar shows which page is being processed. Avoid compressing 100-page documents on a slow mobile device — it can run out of memory.
Privacy: no server uploads
All processing happens entirely in your browser. Your PDF file is never sent to any server. Once the tab is closed, nothing is retained. This makes the tool safe for confidential documents, contracts, and financial reports.
After compressing: next steps
If you need to combine the compressed PDF with others, use the PDF Merger to combine them into one document. If your goal is reducing a portfolio of images for the web, use the Image Compressor instead — it preserves full image quality with no rasterization trade-off.
Compress your PDF in seconds — no uploads, no signup, 100% private:
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