MIME Detector

Detect a file's real type from its magic-number signature and compare it to the declared type — useful for spotting mislabelled files. Only the first bytes are read, locally.

How to use MIME Detector: Open MIME Detector — it runs entirely in your browser with no setup. Paste or type your input into the text area, or upload a file where supported. Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server. Everything runs inside your browser, so your data never leaves your device.

Click or drop any file to detect its true type

Only the first 16 bytes are read, locally — the file is never uploaded.

Detect a file's real type from its magic-number signature and compare it to the declared type — useful for spotting mislabelled files. Only the first bytes are read, locally. MIME Detector is a free, browser-based tool in the Filevane developer tools collection — there is nothing to install, no account to create and no watermark on your results. It works on desktop, tablet and mobile, and because the work happens on your own device it stays fast even with large inputs.

How to use MIME Detector

Open MIME Detector — it runs entirely in your browser with no setup.
Paste or type your input into the text area, or upload a file where supported.
Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server.
Review the output instantly; large inputs are handled locally without lag.
Copy the result to your clipboard or download it. Your data never leaves the page.

Why use MIME Detector?

100% free with no limits, no sign-up and no watermarks.
Private by design — your data are processed in your browser and never uploaded to a server.
Fast and lightweight, with instant results even on a phone or a slow connection.
Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
Part of a full developer tools suite, so related mime detector tasks are one click away.

What people use MIME Detector for

Finding out what a file actually is when the extension is missing or wrong.
Validating an upload before processing it, rather than trusting its name.
Identifying an unknown file recovered from a backup or a download.

MIME Detector: limits and things worth knowing

Detection reads the file's magic bytes — the signature at the start of the file — so it identifies the real format regardless of what the file is called. PNG begins with the bytes 89 50 4E 47, PDF with %PDF, and ZIP with PK.
Modern office documents and EPUB files are ZIP archives underneath, so they all share the PK signature and are distinguished by their internal structure rather than by the first four bytes.
Only the file's leading bytes are read, so identification is fast even on very large files.
The file is read by your own browser and never uploaded, which is what makes it safe to identify a file you do not yet trust.

Is it private and secure?

Your privacy is built in. MIME Detector runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Is It Safe to Paste Production Data Into Online Tools? — JWTs, API responses and env files get pasted into online formatters every day. Here's what actually happens to that data and how to check before you paste.

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