Are online document scanners safe? What to check
Documents are among the most sensitive files people handle — contracts, IDs, medical records, payslips. So the caution is justified: when a website offers to "scan" or "convert" your document, where does the file actually go? The answer separates online scanners into two very different categories.
Server-side vs browser-side tools
Most classic web converters upload your file to their server, process it there, and send back the result. Your document then exists — at least temporarily — on infrastructure you know nothing about, governed by a privacy policy you probably did not read. Browser-side tools work differently: the page ships the processing code to your device, and the computation runs locally. The file never crosses the network at all.
How to tell which one you are using
Signals of browser-side processing: the tool works after you disconnect from the internet (load the page, then switch to airplane mode and try); processing is instant even for large images, with no upload progress bar; and the site says so explicitly. Scandut is browser-side by design — detection, correction, enhancement and PDF assembly all run in your browser, which you can verify with the airplane-mode test.
Sensible rules for sensitive paper
For IDs, contracts and anything with account numbers: prefer a tool that processes locally, or your phone's built-in scanner. Avoid tools that require an account just to convert one file. And whatever tool you use, check the output before sharing it — the most common privacy leak is not the scanner but sending page two of a PDF you forgot contained your salary.