FileType Sniffer — How to Use

FileType Sniffer is a free browser-based tool that reads file Magic Numbers and estimates the real file format.

This tool estimates file format only. It does not verify safety or whether a file is okay to open. Avoid opening files from unknown sources.

1. What this tool does

• Estimates a file format from its first bytes.
• Warns when the extension and detected format do not match.
• Adds notes for ZIP-based containers such as DOCX, XLSX, PPTX, APK, JAR, and EPUB.
• Shows stronger caution for executable or installable formats such as EXE, ELF, Mach-O, APK, and JAR.

2. Steps to use

• Drag and drop a file, or select one manually.
• The tool analyzes it automatically. Press “Analyze” again if needed.
• Check the summary and JSON output for detected format, MIME type, confidence, and matched bytes.
• If a mismatch or executable warning appears, avoid opening files from unknown sources.

3. Supported / Unsupported

Main supported formats:

• PDF / PNG / JPEG / GIF / WebP / AVIF / HEIC / HEIF
• ZIP / 7Z / GZIP / RAR
• MP3 / WAV / MP4 / MOV / WebM / MKV
• BMP / TIFF / ICO
• EXE / ELF / Mach-O

Limitations:

• The tool does not inspect full file contents or verify safety.
• ZIP-based container notes are mainly extension-based; full ZIP internal filename inspection is not performed.
• Encrypted, custom-header, or heavily corrupted files may be shown as Unknown.

4. Error types

• No file selected: choose a file first.
• Read error: the browser could not read the selected file.
• Unknown: the file did not match known Magic Number patterns.

5. Output format

• Bytes read: only the first 4096 bytes are read.
• Detected type: estimated from Magic Number patterns.
• MIME type: representative MIME for the detected format.
• Match: relationship between the filename extension and estimated format.
• What to check next: practical caution before handling the file.

6. FAQ

Q. Can this tool perform a security scan?
A. No. It estimates the file format only and cannot determine whether a file is safe.

Q. Why are DOCX or XLSX files treated as ZIP?
A. Some Office documents use a ZIP-based container structure.

Q. Are files uploaded?
A. No. The tool reads only the first bytes inside your browser.

7. Disclaimer

This tool only estimates file formats based on Magic Numbers. Results and safety are not guaranteed. Verify important or unknown files through trusted methods.

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