FILE TOOL // 044

Magic Number Identifier

Compare a file's leading byte signature with common format patterns, then flag disagreements with its extension or browser-reported MIME type.

Processed locally in your browser

Choose files to identify

Common signatures checked locally

Drop files here Select files whose real leading bytes you want to compare with known magic-number patterns.

FileSizeType

No files selected.

Scan depth Unknown handling Filename comparison Report format

Include leading hex

Choose files to begin.0 files

How to use Magic Number Identifier

Select files whose real leading bytes you want to compare with known magic-number patterns.
Adjust the options for the report you need.
Select “Identify Formats,” review the result, and download the generated file.

What this file tool does

Compare a file's leading byte signature with common format patterns, then flag disagreements with its extension or browser-reported MIME type.

The tool reads the leading bytes and checks exact signatures for common formats including PDF, PNG, JPEG, GIF, ZIP-family, GZIP, 7z, RAR, ELF, WebAssembly, OGG, FLAC, MP3, TIFF, BMP, and SQLite.

Processing stays on this device. Signature coverage is intentionally finite. ZIP-based formats share a container signature and may require deeper package inspection.

Supported inputs and limits

Signature coverage is intentionally finite. ZIP-based formats share a container signature and may require deeper package inspection.

Signal	Magic bytes, extension, browser MIME
Coverage	Common binary formats
Unknown files	Reported without guessing
Output	JSON or CSV

Example and practical tips

Practical example

A file named report.pdf that begins with PNG bytes will be identified as PNG and marked as an extension mismatch.

Tips

Treat 'unknown' as no matched signature, not as an invalid file.
ZIP signatures also appear in DOCX, XLSX, PPTX, APK, and other containers.
Use a dedicated parser when the exact subtype matters.

Frequently asked questions

How do I identify a file by its magic number?

Choose the file and run the scan; the tool compares its leading bytes with known binary signatures.

Why does a DOCX file appear as ZIP?

DOCX is a ZIP-based container, so its outer magic bytes match ZIP.

Can a renamed executable be detected by its header?

Known executable signatures such as PE, ELF, and Mach-O can be recognized even when the extension changes.

What does unknown magic number mean?

It means none of this tool's supported patterns matched; it does not prove the file is corrupt.

Can file signatures be forged?

Yes. Magic bytes are useful evidence but can be imitated, so they are not a security guarantee.

Related file tools

File Header Inspector File Entropy Analyzer Embedded Strings Extractor Null Byte Scanner

Magic Number Identifier details

Tool number	044
Category	File Inspection & Analysis
Processing	Local browser operation
Download	Generated report or verification bundle

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