Detect an image's real format from its file signature bytes, not from its file name.
Try an example
Load a ready-made sample into this tool and run it. Every result you see is calculated live by the tool itself — nothing here is a pre-written answer.
Sample: File: sample-photo.jpg
How to Use
- Choose any file (up to 10 MB).
- Click Run.
- Read the detected format and whether the extension matches.
Detecting a file's real format from its signature
This image format detector reads the opening bytes of a file — its signature — and reports the format those bytes actually describe, regardless of the file name. Choose a file, click Run, and see the detected format and whether the extension matches. Use the image format detector when a file's name and its behavior disagree. The answer comes from the file itself.
When the extension cannot be trusted
Use it for downloads that will not open, attachments renamed by other software, or files from a camera or scanner with odd naming. Knowing the real format tells you which program or converter you actually need, instead of guessing from a possibly wrong extension. It works even when the extension is missing entirely.
Good to know
Detection covers common signatures: PNG, JPG, GIF, WebP, BMP, ICO, PDF and ZIP. A file outside those types, or one too damaged to read, is reported as unknown rather than given a guessed label it has not earned. Files up to 10 MB can be checked.
Frequently asked questions
What does it mean when the extension does not match?
It means the file's contents are a different format from what its name claims — for example, PNG data in a file named .jpg. Renaming it to the detected format usually lets the right programs open it.
Can it identify any file I give it?
It recognizes the common signatures listed on this page and reads files up to 10 MB. Anything else is reported as unknown. It identifies the container format from the first bytes; it does not inspect the file's full contents.
Is my file uploaded anywhere?
No. Only the opening bytes are read, inside your browser, and the file is never sent to this site's server. Documents and images are identified without leaving your device.
How to use Image Format Detector
- Choose any file (up to 10 MB).
- Click Run.
- Read the detected format and whether the extension matches.
Limitations
Detection covers common signatures (PNG, JPG, GIF, WebP, BMP, ICO, PDF, ZIP); unknown files are reported as unknown. Files are processed in your browser and never sent to the site's server.