How can I determine file type without an extension on Windows? (2025)

181

You can use the TrID tool which has a growing library of file type definitions for identifying files with.

Wildcards are supported, so in your example you could just put all the images to be examined in a folder, e.g. C:\verifyimages - then you can use the command:

trid C:\verifyimages\*

This will examine all files in the verifyimages folder.

There is also a GUI version available, TrIDNet:

There is documentation available on how you can you can easily integrate TrID or TrIDNet into Windows Explorer and Total Commander:

Windows Explorer

• Integrate TrID
• Integrate TrIDNet

Total Commander

• Integrate TrID
• Integrate TrIDNet

• 8

  Do note that it indicates it is not licensed for commercial use, only personal use

  –Chris Magnuson

  Commented Jan 31, 2015 at 17:31

• 6

  I had some trouble figuring out which download files were necessary to use this program. So this comment is to aid in that. You'll need to download two files. First, either the command line utility or the GUI utility. Second, a folder of XML definitions called "TrID XML defs". Place the definition XML files in the same directory as TrID. Then scan definitions. Finally you can start using it.

  –mrtsherman

  Commented Mar 26, 2015 at 15:40

• Thanks, mrtsherman, for the clarification. I was confused as well. Docs could be improved, but nice tool!

  –Woodchuck

  Commented Oct 6, 2018 at 17:26

• 1

  For info, there is an online version at mark0.net/onlinetrid.html

  –Wok

  Commented May 25 at 13:13

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58

file

File tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic number tests, and language tests. The first test that succeeds causes the file type to be printed.

The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually “binary” or non-printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data.

• 1

  file is standard, but on older systems (especially non-Linux) not very knowledgeable. For Ubuntu etc it should be quite respectable and even installed as standard.

  –Thorbjørn Ravn Andersen

  Commented Apr 24, 2011 at 13:28

• 2

  I very much doubt that file is an expert on files made by Windows applications.

  –Robin Green

  Commented Apr 24, 2011 at 20:23

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  @Robin: You're welcome to test it.

  –Ignacio Vazquez-Abrams

  Commented Apr 24, 2011 at 20:27

• 13

  @Robin: I very much doubt you've used file at all, and yet you've almost made up your mind about its effectiveness.

  –tzot

  Commented Apr 24, 2011 at 23:24

• 2

  @Gqqnbig, that version of file.exe is a decade old and overall status of gnuwin32 is unmaintained since 2013 as per Wikipedia. The modern approach is to use git-for-win: git-scm.com/download/win, that bundles Unix utilities (latest versions). After installation, you should have %ProgramFile%\Git\usr\bin in PATH with file.exe in it. For Windows 10 you may also enable Windows Sybsystem for Linux (WSL), install a distro of your choice (ubuntu, fedora, alpine, gentoo, etc.), enter it and do file /mnt/c/your/path/in/windows/filename.extension (/c/ part represents C: drive).

  –vulcan raven

  Commented May 25, 2019 at 10:57

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16

I used to work for the French National Library, to build an digital archive system that contains not only digitized books but also millions of digital artefacts with all kinds of strange file types. We used JHOVE to recognize file formats.

JHOVE is open source, it is maintained by JSTOR and the Harvard University Library. It is rather simple to use.

• cool! but does it recognize proprietary formats like TrID does? anyways, I do have some uses to identify subformats/variants of non-proprietary formats (or, to be precise, proprietary 'extensions' to standardized formats), so this would come in handy. thank you for the heads-up!

  –pepoluan

  Commented Apr 24, 2011 at 14:00

• It doesn't have support for most formats. Imho pretty useless tool, if you don't want to identify any of it's few known file types.

  –crash

  Commented Sep 19, 2023 at 12:52

• I know this answer is 13 years old by now, but even 13 years later this software still only supports identifying 17 file formats, whereas the tool TrID listed above currently identifies 18,234 file types. It's worth noting that the two tools serve different functions. TrID exams the "magic number" of the file (first couple bytes which identify filetype). JHOVE will examine the formatting, so where TrID sees an ASCII/Text file JHOVE might see it is an .xml or .html file.

  –ShaneB

  Commented Oct 3 at 17:04

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12

A modern approach that may appeal is to use Git for Windows. Run git-bash.exe and run the command file path\to\file. An example output might be:

TestFile.ico: MS Windows icon resource - 1 icon, 128x128, 32 bits/pixel

Alternatively, use the command file -i path\to\file, which might give:

TestFile.ico: image/vnd.microsoft.icon; charset=binary

• 1

  Thank you! At least I can get the mime types and construct an mv batch to fix the file extensions. Perhaps someone with more time can automate the process into a program :)

  –ADTC

  Commented Mar 23, 2021 at 17:22

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3

You can check the file type from any computer including windows at

http://www.checkfiletype.com

• 3

  Welcome to Super User! Please read how to recommend software in answers, particularly the bits in bold; then edit your answer to follow the guidelines there. This applies even though you are recommending a website! Cheers

  –bertieb

  Commented Jun 4, 2018 at 11:33

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2

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