How to check if a PDF site uploads your file

The test, step by step

1. Open the tool in a desktop browser and press F12 (or Ctrl+Shift+I) to open the developer tools. Choose the Network tab.
2. Click the clear button in the Network tab so the list is empty, and tick Preserve log if you see it.
3. Choose a small, non-sensitive test file and run the tool: convert, compress or whatever the page does.
4. Look at the list of requests. Click any request that uses POST or PUT, and open its Payload or Request tab. If your file is being uploaded, you will see a large request carrying the file's contents, and its size will be close to the size of your file.
5. Compare sizes. Sort the list by size. A tool that uploads a 5 MB file must send roughly 5 MB somewhere.

What you should expect to see on a browser-only tool

• Small requests for analytics, advertising and page scripts. These are normal, and they do not contain your document.
• On FreePDFScanner, the text-recognition engine files are downloaded from FreePDFScanner itself the first time you use OCR. That is a download to your device, not an upload of your file.
• No request whose size matches your file.
• If you accept analytics cookies, FreePDFScanner sends usage events such as which tool was opened. If you accept session recordings, Microsoft Clarity may record page interactions, with pages that show your documents masked. The Network test checks whether your file is uploaded; it does not show everything a page might record, so read the privacy policy too.

A second check: go offline

Load the tool, then turn off your internet connection (airplane mode, or the Offline setting in the Network tab) and run it on your test file. A tool that works in your browser can often still process the file. A tool that needs a server will fail. This is a hint rather than proof, because a tool might need to fetch extra files the first time it runs, so use it alongside the Network check.

When a file is deliberately sent

Some features are meant to store a file. On FreePDFScanner, the scanner has a Save to account button. It asks you to sign in, and when you choose it, the PDF you created is sent to your account's private storage, because that is the point of saving it. Nothing is saved unless you choose that button. The tools that process a file locally do not upload it.

Check any site's privacy policy as well. It should say which features use a server and which do not. Ours is at /privacy.

Be careful with sensitive files

• Test with a harmless file first, not your passport or contract.
• Browser extensions can read what you open. Use a private window with extensions off for sensitive documents.
• If a site asks you to upload a file and you cannot tell what happens to it, use software installed on your own device instead.