How I check whether a "no upload" PDF tool really keeps my file local
Lots of PDF and image sites now say "your file never leaves your device". Some of them mean it, and some run the work on a server anyway. You don't have to take the label on trust: the browser can show you every request a page makes, and you can cut the network and see whether the tool still works. Below are the exact steps in Chrome or Edge (Firefox where it differs), what each check can and…
When evaluating whether a no-upload PDF tool truly keeps your file local, you can rely on two checks using the browser's built-in tools. First, open the tool's page and inspect the Network panel. Look for POST or PUT requests made during the upload process. In the Headers section, check the Request URL and Method to confirm it's a POST request.
In the Payload section, you should see the file being sent as form data. The Initiator column shows which script started the upload. Remember that the Size column in the Network panel represents the size of the downloaded response, not the data sent. To avoid missing uploads, don't filter by size. Use the Offline setting in Chrome DevTools (Disable cache > Offline) to simulate local processing.
This ensures any upload happens immediately after the page loads. However, these checks have limitations. They only capture behavior during your immediate session and can't reveal future sends, small pieces of data, or WebSockets. Also, extensions or external tools aren't visible in the Network tab.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
