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Almost every PDF site promises that your files are safe. But does your document go to a server, or does it stay on your device? You don’t have to take anyone’s word for it: your browser shows you. These tests work on any website, including ours.
Test 1: the network tab (on your computer)
- Open the PDF tool in Chrome, Edge or Firefox on your computer.
- Open the developer tools with F12 (Mac: ⌥ ⌘ I) and choose the Network tab. Also turn on the option that keeps the log (“Preserve log” or “Persist Logs”), so nothing disappears when the page changes.
- Use the tool as usual: choose a PDF of a few MB, process it and download the result.
- Look at what was sent. Look for requests with the method POST or PUT. Click one and check Payload (Firefox: Request): if you see your file or its file name there, it was sent. Sending a large file takes a while, so such a request also stands out as a long bar in the timeline (Waterfall).
A tool that works locally only loads the page, the scripts and possibly statistics. Those requests are small and don't contain your file. A tool that uploads sends your PDF in a POST or PUT request, sometimes in chunks, sometimes over a WebSocket (filter WS).
Test 2: airplane mode (on your phone too)
- Open the tool and wait until the page has fully loaded. You can already choose your file if you like.
- Turn off your internet: switch on airplane mode, or turn off wifi and mobile data.
- Process your file. If it works and you can download the result, the work happens on your device. If you get an error or the tool hangs, it needs a server.
- Close the tab before you go back online. That reduces the chance that the site sends something afterwards; if you want to be sure, keep the network tab open when you reconnect.
Other signs of an upload
- You see a progress bar saying “Uploading…” before processing starts.
- Your result is available through a download link that expires after a while, or that you receive by email.
- The site promises your files will be “deleted after an hour”. Whatever has to be deleted was on a server first.
- On a slow connection, large files take noticeably long, even though the processing itself should be quick.
Reading a privacy policy is useful, but it’s still a promise. The network tab shows what really happens.
On Verify it yourself you can see step by step what the network tab shows on PDFCommunity: the page, the PDF libraries, a cookie-free visitor counter, and Google Analytics if you accepted it in the cookie banner. Not your file.
Frequently asked questions
Is an upload always a problem?
Not necessarily. Many services delete files properly after processing. But you have to trust that this happens, and with documents that contain personal data, such as contracts or medical and financial documents, you’d rather avoid that extra data flow.
Can I check this on my smartphone too?
The developer tools are hard to reach on a smartphone. The airplane mode test does work there: load the page, switch on airplane mode and process your file.
A tool works offline. Is that a guarantee?
It shows that the processing itself happens on your device. In theory, a site could store data and send it later. That’s why you should close the tab before going back online, or keep the network tab open when you reconnect.