How to check whether a scanner uploads your documents

Every scanning site says comforting things. Rather than parsing privacy-policy prose, run one of these two tests — they take minutes and produce facts.

Test 1: airplane mode (anyone, any phone)

1. Open the scanning site and let it load fully.
2. Turn on airplane mode (kill Wi-Fi too).
3. Try to scan a harmless page — a shopping list.
4. If it completes offline, processing is local. If it spins, errors or “can't reach server”, your documents were going to travel.

ToPDF passes this after its first visit — try it.

Test 2: watch the network (5 minutes, any computer)

1. Open the site in Chrome/Edge/Firefox, press F12 → Network tab.
2. Clear the log, then scan a test page.
3. Look at the requests during the scan. Downloads of the app's own files are normal. What you're looking for is uploads: POST/PUT requests with large payloads leaving right after you pick the photo.
4. Large outbound request ≈ your document leaving. None ≈ on-device.

Reading privacy policies faster

Two phrases tell you the architecture instantly: “files are automatically deleted from our servers after…” = server-side. “processed locally / on your device / never uploaded” = on-device (verify with test 1). Absence of any statement about file handling is its own answer.

Frequently asked questions

Could a tool upload later, after I go back online?

A malicious page could try, which is why the network-tab test matters and why using tools with a visible, verifiable architecture beats trusting any single test. ToPDF keeps no copy of your scan to upload later — the page holds documents only while you’re working on them.

Do these tests work for phone apps too?

Airplane mode does. The network tab needs a computer, but an app’s offline failure is the same tell: cloud processing.