About Compress PDF
Compress PDF — free, private, browser-based pdf tool
Make a large PDF small enough to email or upload. Pick Light, Balanced or Strong and download the result — the file is processed in your browser and never uploaded.
Why use Compress PDF
- ·Files stay on your device — nothing is uploaded
- ·No signup needed
- ·Works in any modern browser, on any OS
- ·Free daily use; Pro removes limits and watermarks
How to use it
- 1Drop the PDF you want to shrink.
- 2Choose Light, Balanced (default) or Strong, and tick Grayscale for black-and-white documents.
- 3Download the compressed PDF and check the new size shown next to the original.
How the compression works
Each page is rendered and re-saved as a JPEG image, then the PDF is rebuilt from those images. Light keeps pages up to 2200 px on the long edge, Balanced (the default) 1700 px and Strong 1300 px, with image quality stepping down from 82% to 60%. A grayscale option saves more on colour scans.
When to use it — and when not to
It works best on scans, photo-heavy brochures and exported slide decks, where the images are what make the file big. Because every page becomes an image, text in the result can no longer be selected or searched; keep the original if you need that.
How it works
pdf-lib and pdfjs-dist render and edit the PDF stream directly in your browser. Tesseract.js handles OCR with on-device language packs. The processing code runs inside the page, so your file is not uploaded to a server — you can confirm this in your browser's DevTools → Network tab.