What Happens to Your Files When You Use an Online PDF Tool?

Every PDF tool website makes claims about your files. Some upload them to servers; some genuinely don't. Here's how to tell the difference — and why it matters.

Server-based processing

Most online PDF tools work like this:

1. You choose a file.
2. The browser sends it to their server.
3. The server processes it and sends the result back.

Your document is now on someone else's infrastructure — even briefly. It may be logged, stored, or scanned by automated systems.

Browser-based (local) processing

Tools like FreePDFToolbox work differently:

1. You choose a file — it is read by JavaScript in your browser.
2. Processing libraries (like pdf-lib and pdf.js) run on your device, compiled to WebAssembly.
3. The result is generated locally and you download it.

At no point does your file travel over the network.

How to verify any tool yourself

1. Network tab test — open DevTools → Network, then run a tool. A local tool makes zero requests carrying your file.
2. Offline test — load the page, disconnect the internet, and process a file. Local tools keep working.
3. Look for the words — genuine local tools say 'processed locally in your browser' and mean it.

What this site does

• All 50 tools process files locally.
• No file data is ever sent anywhere.
• No accounts, no analytics, no tracking scripts.
• The site is fully static — nothing runs on a server at all.

Frequently asked questions

Do local tools work offline?

Once loaded, yes — processing is pure client-side.

Are local tools slower?

Sometimes — your device does the work. For most files the difference is unnoticeable.

Is local processing always better?

For privacy, yes. Server tools may add features (like large-scale OCR), but they cost you control over your files.

See the full comparison in Are Online PDF Tools Safe?.