FREE · FILE, OFFICE & SPREADSHEET CONVERTERS
File Type Identifier (Magic Number).
Find out what a file really is from its first bytes — PDF, image, video, archive, Office document, program and 50+ other types — and spot renamed or disguised files.
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How to use File Type Identifier (Magic Number)
Choose any file. Only its first 64 KB are read, in your browser, and compared with known signatures.
How it works
Each format starts with characteristic bytes (“magic numbers”): %PDF for PDF, 89 50 4E 47 for PNG, PK plus word/ for DOCX, MZ for Windows programs. The extension is then compared with the content.
Example
A file named invoice.pdf.exe starting with “MZ” is reported as a Windows program with a double-extension warning.
Questions about File Type Identifier (Magic Number)
Is File Type Identifier (Magic Number) free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
Text formats (CSV, Markdown, source code) look alike and are reported as plain text. Not an antivirus. Everything is calculated in your browser; nothing you type is uploaded. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.