File Type Detector (Magic Bytes)
File
Reads the first 512 bytes of any dropped file in the browser and matches them against a table of ~35 well-known file signatures (PNG, JPEG, GIF, WebP, PDF, ZIP, GZIP, 7z, MP3, FLAC, MP4, MKV, WOFF2, ELF, PE, SQLite, …). Compares the detected type against the browser-reported MIME (which comes from the OS, usually from the extension) and flags mismatches — useful when checking downloaded archives, verifying that a renamed .jpg really is a JPEG, or sanity-checking user-uploaded files before processing.
How to use
- Drop or pick any file.
- Read the detected type — if it disagrees with the declared one, the badge will tell you.
Frequently asked questions
- Does the file leave my browser?
- No. Only the first 512 bytes are read, and only locally through the File API. Nothing is uploaded.
- Why does a .docx come up as ZIP?
- DOCX, XLSX, PPTX, JAR, EPUB, and OOXML are all ZIP containers under the hood. To distinguish them you'd need to inspect a specific entry inside the archive — magic-byte detection alone can't tell them apart.
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