File type inspector
Identify what a file really is from its own bytes, and see the first 256 in hex.
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About this tool
Drop in a file and find out what it actually is, read from the magic bytes at the start of the file rather than from its name. Around fifty formats are recognised — images, archives, PDFs, audio and video containers, fonts, databases and executables — and the tool says so plainly when a file called .jpg turns out to be something else. You also get the size, the browser’s reported media type, any byte-order mark, and a hex and ASCII dump of the opening bytes. Only the first few kilobytes are ever read, so any size of file is fine and none of it leaves your device.
Using this tool
Why does my .docx say it is a ZIP archive?
Because it is one. Word, Excel, PowerPoint, OpenDocument, EPUB and JAR files are all ZIP containers with a particular set of files inside, so they share the ZIP signature. The tool lists those extensions alongside the ZIP result rather than pretending to know which it is.
Is a mismatched extension a sign of malware?
Not on its own — renaming files is common and harmless. It is worth attention when the file came from someone you did not expect, particularly if it claims to be a document and is really an executable.
Is there a size limit?
No. Only the first four kilobytes are read, so inspecting a 20 GB disk image costs the same as inspecting a text file and uses no meaningful memory.
Tool activity
Simple tools for everyday work.
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