Image Format Detector

About Image Format Detector

The Image Format Detector identifies the true format of any file by reading its magic bytes (also called file signatures). Unlike relying on file extensions, which can be easily renamed or stripped, magic bytes are embedded at the binary level of every file and uniquely identify the file type.

This tool supports detection of all major image formats including JPEG, PNG, GIF, WebP, BMP, TIFF, ICO, SVG, AVIF, HEIC, and PSD, as well as PDF documents. It reads the first 16 bytes of your file and compares them against known format signatures to determine the true file type.

All analysis is performed entirely in your browser — your files are never uploaded to any server. This makes it safe for sensitive or private files. The tool also compares the detected format against the file extension to alert you of any mismatches, which can indicate renamed files, potential security concerns, or upload errors.

What Are Magic Bytes?

Magic bytes are a sequence of bytes at the beginning of a file that identify the file format. For example, all JPEG files start with FF D8 FF, and all PNG files start with 89 50 4E 47. Operating systems and applications often rely on file extensions to determine file type, but magic bytes provide the ground truth.

Common Use Cases

• Verify that downloaded files are the correct format before opening
• Detect files that have been renamed to bypass upload restrictions
• Identify unknown files without an extension or with a wrong extension
• Security auditing to find disguised executable or script files
• Debugging image upload issues caused by format mismatches