How to tell if a website uploads your file (Network tab, two minutes)

Most "free PDF" and "free converter" sites take the file. They say they delete it later. You do not have to take that on faith.

This is the check I use. It works on any site, including mine.

Setup

1. Open the converter in Chrome or Edge.
2. Press F12 (Mac: Cmd + Option + I).
3. Click Network.
4. Check Preserve log.
5. Click the clear-circle icon so the list is empty.

Leave that panel open.

Run it

Drop a file you do not care about. A 2–3 MB photo is easy to spot. Watch the list while the tool works.

What an upload looks like

Ignore most of the GETs. Those are the page fetching JS, WASM, fonts, ads.

An upload is usually:

• Method: POST or PUT
• Size: close to your file. A 3 MB photo makes a ~3 MB request.
• URL: something like /upload, /api/convert, or an S3 / GCS host.

Click that row → Payload. If you see the file, it left the machine.

What local processing looks like

After you add the file, you should not see a request near the file's size. You may see the page download a WASM engine before you pick a file. That is code coming in, not the document going out.

Size is the tell. Method is the second tell.

Two traps

Ads and analytics. AdSense and GA fire requests. They are small. They are not a 3 MB PDF.

Turning Wi-Fi off. Only useful after the page and its engines have finished loading. If you cut the network too early, a local tool looks broken because the WASM never arrived.

Why this is better than a privacy policy

A policy is a promise. The Network panel is a log. If the site has no upload endpoint, there is nothing to argue about.

I keep the longer writeup, with screenshots, here:

https://imissfiles.com/guides/check-if-a-website-uploads-your-file/

I also run a suite of in-tab PDF and image tools on the same domain. Affiliation: I built it. Same test applies there. Ads are on the page. They do not receive the file.