PrivTab

File Type Detector

Find out what a file really is, even when it has no extension or the wrong one.

Runs in your browser · No uploads

Drag & drop files here

or

Any file type, one or many. Only the start of each file is read.

Your files stay on your device. Nothing is uploaded.

  • Nothing leaves your device
  • No server-imposed size limits
  • No sign-up, no watermark
  • Free

How to identify a file type

  1. Choose one or more files.
  2. Read the detected type, category, MIME type and usual extension.
  3. Compare it with the file's current extension.

How it works

Most formats start with a fixed signature, sometimes called magic bytes. The tool reads the start of the file, compares it with about 80 known signatures and shows the first bytes so you can check them yourself. Plain text formats such as JSON, CSV, HTML and SVG are recognized from their content.

Safety tip

A file that claims to be a document or photo but is detected as a Windows executable deserves caution. Do not open it.

Is my file uploaded?

No. Your file is processed locally in your browser and never leaves your device. This site has no upload feature, and its security policy blocks the page from uploading anything.

Frequently asked questions

Can it identify every file?

It recognizes common formats. Rare or proprietary formats may be reported as unknown binary data.

Does it read the whole file?

No. Only the first 64 KB are read, so even huge files are checked instantly.

Is my file uploaded?

No. Detection runs in your browser.

Guides for this tool