What is File Type Identifier?

File Type Identifier detects the true format of any file by reading its binary signature (magic bytes) — not just the extension. Useful for identifying renamed or extensionless files and verifying that a file is what it claims to be.

Drop one or many renamed or extensionless files and the page reads the leading bytes — the so-called magic number — then matches that fingerprint against a library covering PNG, JPEG, HEIC, AVIF, PDF, ZIP, MP3, MP4, ELF, and dozens more. ZIP-based files are peeked inside to reveal the real format (DOCX, XLSX, APK, EPUB, JAR, OpenDocument) and list their members. Known ransomware extensions and header markers raise a visible warning, and headers that satisfy two formats at once are flagged as polyglots. Each result shows the real MIME type, the canonical extension, a detection-confidence score, a full SHA-256 fingerprint, and a hex+ASCII dump of the header — plus an optional TXT or JSON report, all computed on your device with nothing uploaded.

How to use

1. Step 1 — Drop or select a file whose type you want to identify.
2. Step 2 — The tool reads the file's binary header and matches it against known signatures.
3. Step 3 — View the detected MIME type, file extension, and a description of the format.

When to use

• Investigating a download named report.txt that won't open as plain text.
• Triaging an email attachment with a suspicious or missing extension before opening it.
• Confirming an exported file is the format you asked for (e.g. real JPEG, not BMP renamed).

Result

A colleague sent 'report' with no extension: drop it in and you'll see it's actually a PDF (application/pdf), so rename it to report.pdf and open it normally.

FAQ

Why don't you just trust the file extension?

Extensions are easy to change by accident or on purpose. A file called photo.jpg might really be a PNG, a PDF, or even a ZIP archive. The magic number lives inside the bytes and almost always reflects what the file actually is.

Will it detect every file type?

It covers over 50 common formats — images, video, audio, archives, documents, executables, fonts, and databases. Obscure or proprietary formats may show the generic «application/octet-stream» fallback, in which case the hex header is still useful for manual lookup.

Can it tell .docx and .xlsx apart? They're both ZIP files underneath.

Yes. When the outer signature is ZIP, the tool peeks inside the archive and looks for telltale members like word/document.xml (DOCX), xl/workbook.xml (XLSX), ppt/presentation.xml (PPTX), AndroidManifest.xml (APK), META-INF/container.xml (EPUB), or a JAR manifest. The result shows both the base format (ZIP) and the underlying format (e.g. Word Document), plus a short listing of the archive members.

Are the magic bytes the same as a hash or checksum?

Not quite. A hash summarises the entire file; magic bytes are just the first few bytes that act as a format identifier. Two different PNG images share the same magic number but have completely different hashes. The tool shows both — the magic bytes that name the format, and a full SHA-256 hash that fingerprints the exact file.

Does the file leave my device?

No. Type detection reads only the first few hundred bytes and matches them right here on the page. To compute the SHA-256 fingerprint the whole file is read locally, so very large files take a moment, but nothing is ever copied or sent anywhere — every byte stays on your device.

Related Tools