Free · Check whether a file name matches its bytes

File Extension Checker

Find a wrong or missing extension and see the file name that fits the detected type.

  • Real magic-byte check
  • Private in your browser
  • JSON report

Open a local file

The file stays in this browser tab. Detection uses its binary signature, not just its name.

file-type · local
Drop one file hereUp to 100.0 MB

Files stay in this tab. The checker reads bytes but never opens or runs the file.

ResultReading the safe sample
Reading the signatureThe file is not opened or run.

A useful hint, not proof. A matching signature does not prove that a file is complete, valid, or safe. This tool does not scan for viruses.

Three simple steps

How to use it

  1. Open a file with a name you do not trust.
  2. Read the detected and named extensions.
  3. Use the suggested name only after you check the file.

Your files stay on this device

file-type reads the binary signature inside this browser tab. Bookify does not upload, save, open, or run the file. The result is a best-effort hint, not proof that a file is valid or safe.