How does this detect the file type without an extension?

It reads the first bytes of the file and checks them against known "magic number" signatures used by common formats (PNG, JPEG, PDF, ZIP, MP4, and more) — the same technique operating systems use.

Why would a file have the wrong extension?

Often harmless (a renamed file, a download that lost its extension) but sometimes a red flag — malware is sometimes disguised with an innocuous-looking extension, so a mismatch is worth a second look.

Does this tool upload my file anywhere?

No — detection reads the file locally in your browser, nothing is sent to a server.

File Type / MIME Detector

Detect a file's real type from its content and check it against the extension the filename claims.

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Choose a file

Files never leave your device — only the first 1KB is read, entirely in your browser.

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How it works

1
Choose a file

Any file, regardless of its extension.
2
Type detected instantly

Its first bytes are checked against known format signatures.
3
See if the extension matches

A mismatch between the real type and the filename is flagged.

FAQ

How does this detect the file type without an extension?: It reads the first bytes of the file and checks them against known "magic number" signatures used by common formats (PNG, JPEG, PDF, ZIP, MP4, and more) — the same technique operating systems use.
Why would a file have the wrong extension?: Often harmless (a renamed file, a download that lost its extension) but sometimes a red flag — malware is sometimes disguised with an innocuous-looking extension, so a mismatch is worth a second look.
Does this tool upload my file anywhere?: No — detection reads the file locally in your browser, nothing is sent to a server.