File Type Checker
Identify what a file really is from its magic bytes, see its MIME type and catch wrong or disguised extensions such as an .exe renamed to .pdf.
- 100% free
- No sign-up
- Files stay on your device
- Updated
Your result
Results for your file appear here.
How this was calculated
About File Type Checker
File Type Checker reads the first bytes of a file, its signature, to identify the real format regardless of its name. It flags extensions that do not match the content, including programs disguised as documents or photos. Only the first 4 KB are read, on your device.
How to use File Type Checker
- Choose any file.
- Press Check file type.
- Read the detected format, MIME type and whether the extension matches.
Key features
- Recognises 50+ formats: documents, images, audio, video, archives, fonts, executables
- Extension mismatch warning
- Warns about disguised executables
- Shows the first bytes in hex
- Works with files of any size
How it works
The first bytes of the file are compared with known format signatures; the extension is then checked against the result.
File Type Checker examples
Renamed photo
Input: photo.png that is really a JPEG
Result: Detected: JPEG image, with a mismatch warning.
Office file
Input: report.docx
Result: Detected: Word document (DOCX); the extension matches.
Important notes before you rely on the result
- Files are read on your device and never uploaded.
- A matching signature or checksum confirms a file’s format or integrity, not that it is safe. Scan unknown programs with antivirus software.
Limits and supported formats
- Signatures identify the format, not whether a file is safe or valid; damaged files can still match.
- Plain-text formats (CSV, code, Markdown) share no signature and are reported as plain text.
Privacy
Processed on your device. Your files are never uploaded to a server.
File Type Checker: frequently asked questions
Why does a .docx show as ZIP?
Office documents are ZIP archives inside. The tool looks for the Word, Excel or PowerPoint parts to name them; when they are not near the start it reports a ZIP-based format.