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Are online PDF tools safe? How to check if your file is uploaded
Short answer
- Online file tools either upload your file and process it on a server or process it inside your own browser.
- Open your browser’s developer tools (F12) on the Network tab and run a test file: an upload shows up as a request roughly the size of your file.
- For ID scans, contracts and similar files, read a server-based service’s retention and deletion policy before using it.
Why this guide exists
This question is part of why FileLivo was built. Uploading a contract or an ID scan to a free PDF site, there was no way to know which server kept it or for how long. Server-based tools are not automatically unsafe, and many are run responsibly. But choosing a tool knowing how it works is different from guessing.
Two ways tools process files
| Server upload | In the browser | |
|---|---|---|
| Where the file goes | Your device → provider’s server → download | Stays on your device |
| Strengths | Heavy jobs on slow devices; features such as OCR | File never leaves the device; no upload wait |
| Weaknesses | You must trust retention and deletion; upload time | Large files limited by device speed and memory |
| What to check | Retention period, automatic deletion, server location | That there really is no upload |
Note that browser-based tools still download their own code. When you open a tool page, the JavaScript and WebAssembly it needs come to your browser; what matters is that your file does not travel the other way.
Check 1: the Network tab
- Open the tool page in Chrome, Edge or Firefox on a computer.
- Press F12 (Cmd+Option+I on a Mac) and choose the Network tab.
- Clear the list, then run the tool on a harmless test file.
- Look for new requests with the method POST or PUT whose size is close to your file’s size. Those mean the file was uploaded. Small analytics pings and GET requests that load fonts or scripts are not uploads.
Check 2: go offline
Open the tool, run it once on a test file so it loads everything it needs, then switch off Wi-Fi and run it again. A tool that uploads files will fail. Some browser-based tools also fetch extra components at the moment processing starts and can fail offline too, so treat the Network tab as the more reliable check.
Rules for sensitive files
- Test with a blank sample file, never the real document.
- If you have to use a server-based service, find its retention period and deletion terms in the privacy policy. If they are not stated, keep sensitive files away from it.
- Before sending the result to someone else, consider protecting the PDF with a password and removing photo location data.
- For work documents, check whether your organisation’s security policy allows external web tools at all.