How It Works (Technical)
FormFit's PDF compressor uses two open-source libraries that run entirely in your browser:
- PDF.js — Mozilla's PDF rendering engine renders each page to an HTML canvas at your chosen resolution
- pdf-lib — rebuilds a new PDF by embedding each canvas as a compressed JPEG image at your chosen quality level
Your file is processed locally. Nothing is sent to any server. This makes it safe for confidential documents like bank statements, legal files and medical records.
Frequently Asked Questions
How much can I reduce a PDF file size?
PDFs containing scanned pages or photos typically compress by 40–70%. PDFs with mostly text and vector graphics compress less — around 10–30%. The result depends on your PDF's content and your chosen compression level.
Will text still be readable after compression?
Yes. Text is rendered at high resolution (1.2–1.5× scale) before compression, so it remains sharp and clear in the output. Even at High compression, text quality is suitable for reading and printing.
Is my PDF uploaded to a server?
No. Everything runs inside your browser using PDF.js and pdf-lib. Your file never leaves your device. This is especially important for sensitive documents.
Does it work on scanned PDFs?
Yes — scanned PDFs (which are essentially images inside a PDF) compress very well because the images can be re-encoded at a lower quality. You'll typically see 40–70% size reduction on scanned documents.
Is there a file size or page limit?
No server-side limits because there is no server. Very large PDFs (100+ pages or 50MB+) may take longer on older devices — the practical limit is your device's available RAM.