How CuroPDF works

Every tool on CuroPDF runs entirely inside your web browser. No files are uploaded to our servers. No data is collected. Here's exactly how it works.

1. You open a tool

When you visit curopdf.com/merge-pdf (or any tool), your browser loads the page. This includes the HTML, CSS, and JavaScript that make the tool work — just like any other website.

2. You select a file

When you click "Upload" or drag a file into the drop zone, your browser reads the file directly from your computer's storage. The file is loaded into your browser's memory (RAM) — not sent anywhere.

3. JavaScript processes the PDF

Open-source libraries like PDF.js (by Mozilla) and jsPDF run the actual work inside your browser tab. They read, modify, and generate the PDF using your computer's CPU and memory. Our server is never involved.

4. You download the result

The finished file is saved directly from your browser to your device. At no point does the file travel across the internet to our servers. It's as private as using a desktop app.

Verify it yourself

Open your browser's Developer Tools (F12 or Ctrl+Shift+I), go to the Network tab, and watch while you process a PDF. You'll see zero outbound requests containing your file data. The only network traffic is loading the page itself — not your documents.

The libraries we use

PDF.js — Mozilla's open-source PDF rendering engine. Powers reading, rendering, and basic manipulation of PDFs.

jsPDF — Client-side JavaScript PDF generation. Creates new PDFs, merges files, and adds content.

Tesseract.js — OCR engine that runs in the browser. Converts scanned text to editable text without sending images to a server.