File Type Identifier

Drop any file to learn its actual format, regardless of what the extension says. The tool reads the first bytes locally, matches them against a signature database and looks inside container formats to tell similar files apart.

Drop files hereor click to choose. Several files at once are fine. Only the first 64 KB of each file is read, and nothing leaves your browser.
Inspect bytes manually

Paste a hex dump or a hex string (the output of xxd or hexdump -C works as-is).

How it works

Most file formats start with a fixed byte sequence called a signature or magic number. A PNG begins with 89 50 4E 47, a PDF with %PDF, a ZIP with PK. This tool reads only the first 64 KB of each file, compares it against a database of known signatures, and then looks inside container formats to tell a DOCX from a JAR, a WebP from a WAV, or an MP4 from a HEIC.

  • Detects images, video, audio, archives, documents, executables, fonts and databases
  • Looks inside ZIP, RIFF, ISO-BMFF (MP4, MOV, HEIF), EBML and PE/ELF containers
  • Recognises text formats such as JSON, XML, SVG, HTML, CSV, YAML, PEM and scripts
  • Flags files whose extension does not match their content
  • Shows dimensions, versions, architectures and other embedded facts where available

When you need this

  • A download has no extension, or a generic one like .bin or .dat, and you want to know what opens it.
  • An email attachment or upload claims to be a PDF or image and you want to check before opening it.
  • A photo will not open because it is actually a HEIC or WebP that was renamed to .jpg.
  • You are debugging an upload pipeline and need to see what the server actually received.

Frequently asked questions

Is the file uploaded to a server?
No. The file is read in your browser using the File API. Only the first 64 KB is inspected and nothing is sent anywhere.
How can a file's extension be wrong?
The extension is just part of the file name. Renaming photo.heic to photo.jpg changes nothing inside the file, so programs that trust the extension fail while ones that read the signature succeed.
Why does it say 'ZIP' for my Word document?
It should not. DOCX, XLSX, PPTX, JAR, APK and EPUB files are all ZIP archives inside, and the tool opens the archive to identify the specific format. If it stops at ZIP, the archive is probably missing the marker files that identify the inner format.
Can it detect malware?
No. It tells you the real format of a file, which helps you spot an executable pretending to be a document, but it does not scan the contents. Use an antivirus tool for that.