How to find out what kind of file you have
- Choose one or more files, or drop them on the box.
- Read the real type, MIME type, and whether the extension in the name agrees with the contents.
- Use the hex dump of the first bytes to see the signature the result is based on.
Recognised families include images (PNG, JPEG, GIF, WebP, AVIF, HEIC, TIFF, PSD), documents (PDF, Office, OpenDocument, EPUB), archives (ZIP, RAR, 7z, GZIP, TAR, XZ), audio and video (MP3, FLAC, WAV, MP4, MKV, AVI, Ogg), fonts, executables, databases, and text formats such as HTML, SVG, XML, and JSON.
Questions
Is my file uploaded?
No. Only the first 64 KB of each file is read, inside your browser, and nothing is sent anywhere.
How does it know what a file really is?
Most formats start with a fixed sequence of bytes, often called a magic number or signature. PNG files, for example, begin with the bytes 89 50 4E 47. The tool checks the start of the file against a table of over 125 formats, and looks inside ZIP files to tell Word, Excel, EPUB, APK, and JAR files apart.
Why does a file show a mismatch?
The name and the contents disagree. Often it is harmless, such as a photo saved as .jpg that is really a WebP, but a program renamed to look like a picture or a document is a warning sign. Do not open files you did not expect.
Why was my file not identified?
Some formats have no signature at all (raw data, many log or config formats, some game files). Text files are detected by their content instead. If you know the format, open the file in the Hex Viewer to inspect it yourself.
Can a file lie about its type?
A file can start with the bytes of one format and carry something else after them. A signature check is a strong hint, not a security scan, so use an antivirus program for untrusted downloads.
Credits
Built by OneTooling using standard browser features. No third-party code runs on your data.