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Image Format Detector
Identify a file from its real magic bytes instead of trusting the extension.
Detect the real format
Detected: choose a file to begin
Matched signature: —
First bytes: —
File: —
How to use the Image Format Detector
- Choose any file, whatever its extension claims to be.
- The tool compares its first bytes against a table of known image signatures.
- Read the detected format and check whether the extension agrees.
Features
- Identifies JPEG, PNG, GIF, WebP, BMP, TIFF, ICO, AVIF, HEIC, PDF and ZIP
- Reads magic bytes rather than trusting the file extension
- Warns when the extension contradicts the real content
- Shows the matched signature in hexadecimal
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Frequently Asked Questions
Common questions about the free online image format detector.
Choose the file and the tool compares its opening bytes with a signature table, then names
the format it matches.
They are the fixed first bytes that every file format writes, such as the eight byte PNG
signature or FF D8 FF for JPEG.
Extensions are only part of the name, so renaming a PNG to jpg changes nothing about the
actual image data inside.
It compares the detected format with the extension you used and warns when the two disagree.
No. Only the first few kilobytes are read, and that happens entirely inside your browser.
It recognises common container signatures such as ZIP and PDF, but the focus is image
formats.
SVG is XML text, so the tool looks for the svg tag in the first part of the file instead of
fixed binary bytes.
Rename the file to the extension matching the detected format so other programs open it
correctly.
Yes. The detector is fully responsive and works in the browser on phones, tablets and
desktops.
Last updated: October 10, 2026