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MIME Type Lookup

Look up the MIME type for any file extension, search the other way round, and detect a file's real type from its magic bytes.

🔒 Runs in your browser — files never leave your deviceFree · No sign-up

Detect from a file

Drop a file here or click to choose
Any type — the signature is read locally

Only the first few kilobytes are read, in your browser. The file is never uploaded.

Extension MIME type What it is Copy

How to use the MIME type lookup

  1. Type an extension such as webp, a MIME type such as application/pdf, or a word such as "spreadsheet" — the table filters as you type.
  2. Narrow the list with the category chips, then copy either the bare type or a ready-made Content-Type: header.
  3. Not sure what a file really is? Drop it into the detector — the first bytes are read locally and matched against known file signatures.

FAQ

Why does my server send the wrong Content-Type?

Most web servers map extensions to types with a table like this one (mime.types in nginx, mime_module in Apache). If a newer format such as .webp, .avif or .woff2 is missing from that table you get application/octet-stream, and browsers download the file instead of displaying it. Add the mapping to the server configuration.

Does the extension or the content decide the type?

Over HTTP the Content-Type header wins — browsers only sniff when it is missing or generic, and X-Content-Type-Options: nosniff disables that. On disk the operating system usually trusts the extension, which is why a renamed file can look harmless while its signature says otherwise.

Is my file uploaded when I use the detector?

No. It reads the first 4 KB with the FileReader API inside your browser and compares them with a table of magic numbers. Nothing leaves the page.

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