Why does my file have the wrong extension?

It may have been renamed, downloaded oddly, or exported by a tool that mislabels files. The magic bytes reveal what it truly is.

Can you always tell if a file is encrypted?

For PDFs and ZIPs, usually. For 7-Zip, RAR and legacy Office, the only sure way is to attempt to open it.

Is it safe to check an unknown file here?

Yes — we only read the first bytes locally to identify it. We don’t execute or upload it.

How to tell what type of file you really have

A file’s extension is just a label — rename `report.pdf` to `report.zip` and it still is a PDF. When a file won’t open or seems mislabelled, you need its real format.

Here’s how to find it, and how to tell if it’s locked.

Identify your file