About KuroPDF

Privacy-first tools that respect your files

Why KuroPDF exists

Every time you use a cloud PDF tool, your contracts, bank statements, medical records, and personal photos travel to a server you do not control. Most people never think about this because these tools are convenient. We wanted to prove that convenience and privacy are not mutually exclusive.

KuroPDF was born out of a simple frustration: why should editing a PDF require uploading it to someone else's infrastructure? Modern browsers are extraordinarily powerful. With WebAssembly and Web Workers, we can run the same kind of processing that servers do — right on your device, with zero network requests.

How it works

WebAssembly

Heavy operations like PDF encryption (qpdf), image encoding (MozJPEG, OxiPNG, AVIF), and OCR (Tesseract) run as compiled WebAssembly modules at near-native speed.

Web Workers

Processing runs in background threads so your browser stays responsive. Multiple files can be processed in parallel without blocking the UI.

Zero Network

Open your browser's Network tab while using any tool. You will see exactly zero upload requests. Your files never leave your device.

Offline Ready

Install KuroPDF as a Progressive Web App and every tool works without internet. The entire codebase is cached locally after the first visit.

Your files stay private

Your files are processed entirely in your browser and are never uploaded to any server.

This is not a marketing claim — it is an architectural fact. There is no server-side processing infrastructure. The "backend" is your own device. You can verify this yourself using your browser's developer tools.

Because nothing is uploaded, KuroPDF generates zero server-side carbon emissions for file processing. This makes it one of the most environmentally friendly PDF tools available.

Technology stack

  • Frontend: SvelteKit 5, TypeScript, Vite
  • PDF engine: pdf-lib (JavaScript), qpdf (WebAssembly)
  • Image codecs: jSquash (MozJPEG, OxiPNG, WebP, AVIF via WASM)
  • OCR: Tesseract.js (on-device text recognition)
  • Hosting: Cloudflare Pages (static files only — no server compute)
  • Encryption: AES-256 via qpdf WebAssembly build

What we collect

KuroPDF uses minimal, privacy-respecting analytics to understand which tools are popular and how we can improve. We do not collect:

  • Your files or any content from them
  • Personal information or email addresses
  • Cookies for tracking or advertising
  • Any form of user profiling

Read our full Privacy Policy for details.

Get in touch

Found a bug? Have a feature request? Just want to say hello? Reach out to us — we read every message.