File Type Inspector
Detect a file's true type from its magic bytes, regardless of what its extension claims.
TL;DR: File Type Inspector is a free, browser-based tool that lets you detect a file's true type from its magic bytes, regardless of what its extension claims.
Drag & drop any file here
About this tool
Detect a file's true type by reading its magic bytes — the specific byte sequence most file formats place at the very start of the file, independent of whatever the filename extension happens to say. A file renamed from photo.png to document.pdf is still, at the byte level, a PNG image — this tool reads the actual bytes rather than trusting the extension, and reports what the file genuinely is.
Key Features
- Reads the first bytes of any file to identify its true format
- Recognizes common image, archive, document, audio, and video formats
- Shows the actual hex bytes read, not just the conclusion
- Flags when a file's extension doesn't match its detected type
- Works on any file, including ones with no extension or a misleading one
- Runs entirely in your browser — the file is never uploaded
How to Use
- Drag a file in, or click to browse.
- See the detected file type, based on its actual byte content.
When to use it
- Verifying a downloaded file is genuinely the format it claims to be before opening it
- Figuring out what a mystery file with no extension actually is
- Checking whether a file was renamed to disguise its real type
- Confirming an upload or export actually produced the expected file format
- Understanding what magic bytes are and how file-type detection actually works under the hood
Tips & limitations
- A file extension is just a naming convention — nothing stops a file from being renamed with a completely different extension while its actual byte content, and therefore its real format, stays unchanged
- Office formats like .docx, .xlsx, and .pptx are technically ZIP archives internally, so their first bytes are identical to a plain .zip file — this tool correctly reports "ZIP-based" for all of them rather than falsely claiming to distinguish between them from the first few bytes alone
- This checks a fixed set of common signatures — an unrecognized result doesn't necessarily mean the file is corrupt or dangerous, just that its format isn't in this tool's signature list
- Detecting the true file type doesn't tell you whether the file's contents are safe — a genuinely valid PDF or image file can still contain something malicious inside a structurally correct wrapper
How magic byte detection works
| Format | First bytes (hex) |
|---|---|
| PNG | 89 50 4E 47 0D 0A 1A 0A |
| JPEG | FF D8 FF |
| 25 50 44 46 (“%PDF” in ASCII) | |
| ZIP / DOCX / XLSX / PPTX | 50 4B 03 04 (“PK” in ASCII) |
These fixed byte sequences are called magic bytes or a file signature — operating systems, antivirus software, and libraries like this tool all use them as a more reliable way to identify a file’s real format than trusting its extension.
Frequently Asked Questions
- No — it only identifies the file's structural format from its byte signature. A file can be a genuinely valid PDF or image at the byte level and still contain something harmful inside that valid structure; format detection and safety are different questions.
- Because Office Open XML formats (.docx, .xlsx, .pptx) are internally ZIP archives with the exact same starting bytes as a plain .zip file. Telling them apart reliably requires looking inside the archive's file listing, not just the first few bytes — which is why this tool is upfront about the limitation rather than guessing.
- It means the file's signature isn't in this tool's list of common formats — not necessarily that anything is wrong with the file. There are far more file formats in existence than any single tool practically covers.
- No — it only reads the first several bytes to check against known signatures. The rest of the file is never read, processed, or uploaded anywhere.
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Embed This Tool
Add the live File Type Inspector tool to your own website with this snippet — it loads the real, working tool in an iframe, not a static screenshot.
<iframe src="https://nexlove.org/embed/file-type-inspector.html" width="100%" height="600" style="border:1px solid #e2e8f0;border-radius:12px" title="File Type Inspector — NexLove.org" loading="lazy"></iframe>