938+ Formats Indexed
Look Up a File Signature in Seconds
Search by extension, MIME type, or format name to find the primary hex signature, byte offset, risk level, and validation code you need.
Popular Formats
Jump into the most commonly validated file types and compare their primary signatures at a glance.
Adobe Portable Document Format
application/pdf
Primary Hex Signature
25 50 44 46 2D
JPEG Image
image/jpeg
Primary Hex Signature
FF D8 FF
Portable Network Graphics
image/png
Primary Hex Signature
89 50 4E 47
Windows Executable
application/vnd.microsoft.portable-executable
Primary Hex Signature
4D 5A
ZIP Archive
application/zip
Primary Hex Signature
50 4B 03 04
Microsoft Word Document
application/vnd.openxmlformats-officedocument.wordprocessingml.document
Primary Hex Signature
50 4B 03 04
Quick API Start
Use the same data programmatically when you need to validate file uploads, scanners, or ingestion pipelines.
Request any known extension and receive the primary signature, MIME types, offsets, related formats, and language snippets.
curl https://filesignature.org/api/v1/pdf
{
"success": true,
"data": { "ext": "pdf", "hex": "25 50 44 46 2D", "offset": 0 }
}
What Each Record Includes
Primary hex signature
The header bytes used to identify the format.
Offset and MIME types
Useful for validation rules and content detection.
Risk level and examples
Quick context for handling safe, medium, and high-risk files.
What Are File Signatures?
File signatures, also called magic bytes, are fixed byte sequences stored at the start of a file. They reveal the real file format even when the extension has been renamed.
A PDF begins with
25 50 44 46
and a PNG begins with
89 50 4E 47.
This database collects those signatures, their offsets, MIME types,
and risk levels so you can validate files with something more
reliable than the filename alone.
Use Cases
Upload validation: reject renamed executables before they enter a workflow.
Content processing: confirm the real format before conversion or preview.
Forensics & security: compare unknown files against known signatures quickly.
Common Questions
Enough context to decide where to click next without repeating the full explainer above.
Why should I validate files by magic bytes?
File extensions can be renamed. Magic byte checks read the binary header, which makes them more reliable for file validation, upload filtering, and security review.
How many file formats are indexed here?
FileSignature.org documents 938+ formats with primary hex signatures, MIME types, byte offsets, risk levels, and validation snippets.
How do I look up a file signature?
Search by extension, format name, or MIME type. You can browse the reference pages for human-readable details or call the free REST API for programmatic lookups.