Nutter Tools
Nutter Tools

A free toolbox that runs in your browser. A tool for every job.

Your files never leave your device

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  3. File type detector
Your files stay on your device

File type and magic byte detector

Drop a file and learn its real type from signature bytes rather than the extension, with container inspection and mismatch flags.

This tool is in beta

Still being tested. If a result looks wrong, tell us.

Report a problem

Drop files to identify them

Any format · first 64.0 KB read per file · stays on your device

Drop files to identify them from their bytes.

The detector reads signature bytes and looks inside the two big container families: ZIP member names separate DOCX, XLSX, PPTX, JAR, APK and EPUB, and the RIFF form type separates WAV, AVI and WebP. It does not scan file contents beyond the 64 KB window, does not run virus checks, and can be fooled by a file crafted to start with another format's bytes. Plain text has no signature, so CSV, JSON and source code are honestly reported as unrecognized.

Options

Only the first 64.0 KB of each file are read, up to 20 files per pass. The read happens in this tab; nothing is uploaded.

More PDF & file tools

  • Image metadata editor
  • Photo location and metadata
  • ZIP files
All PDF & file tools

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