How to Check Whether a PDF Tool Uploads Your Files

You can check whether a PDF tool uploads your file by watching your browser's network activity while the tool runs. Every browser has built-in developer tools that list each request a page sends. If your document is uploaded, you will see a request roughly the size of your file leaving your computer.

Many websites say that files "never leave your device". This test lets you verify that claim on any site, including this one, without installing anything.

Test 1: watch the Network tab

These steps work in Google Chrome and Microsoft Edge. Firefox is almost identical.

1. Open the PDF tool's page.
2. Open the developer tools: press F12, or Ctrl+Shift+I on Windows and Linux, or Cmd+Option+I on a Mac.
3. Select the Network tab.
4. Tick Preserve log so the list is not cleared if the page changes.
5. Click the clear button (a circle with a line through it) to empty the list.
6. Now use the tool as normal: add your PDF and run the merge, compression or conversion.
7. Watch the list of requests while it works.

What an upload looks like

• A request with the method POST or PUT (add the Method column by right-clicking the column headers).
• A request size close to the size of your PDF. A 4 MB file produces a request of about 4 MB.
• When you click the request and open its Payload or Request panel, content labelled multipart/form-data or binary data.
• Often, a request going to a domain different from the one in your address bar, such as a storage or processing service.

What local processing looks like

• No large outgoing request while the tool is working.
• You may see downloads of program files, such as .wasm or .js files. These are the processing engine coming to your browser, not your document going out. They are often cached after the first visit.
• Small requests for analytics or fonts may appear. Check their size: a few kilobytes cannot contain a multi-megabyte document.

Test 2: switch the internet off

This second test is even simpler and catches anything the first might miss.

1. Open the tool's page and let it load completely. Try the tool once with a harmless test file so all its components are downloaded.
2. Disconnect from the internet: turn off Wi-Fi, unplug the network cable, or in the developer tools Network tab change No throttling to Offline.
3. Run the tool again with a PDF.

If the tool still produces a result while you are offline, the processing happened on your device. If it fails with a network or upload error, it needed a server.

Things that can confuse the result

• Analytics and advertising scripts send small requests on most websites. They are a privacy question in their own right, but they are not your document.
• Service workers can make a site appear to work offline because the page itself is cached. Test 2 still shows whether the processing needed the network.
• Hashes and signatures. Some features legitimately send a small fingerprint of a document, for example to obtain a trusted timestamp. A hash is a short fixed-length value; it does not contain the document.

What you will see on Priya LifePDF

If you run these tests on Merge PDF, Split PDF or Compress PDF, you will see program files downloading when a tool first loads, and no upload of your document. Conversions such as Word to PDF download a larger processing engine the first time you use them, then run locally.

A few tools make a network request of their own, by design. Text to PDF and Add Watermark can download a font file for non-Latin scripts, and Timestamp PDF sends a hash of your document to the timestamp authority you select. In both cases the document itself stays on your device.

For the wider picture of why this matters, read is it safe to upload PDFs to online converters?