If you have a file with an extension you don't recognize and need information on what type of file is represented by that particular extension, you can go to The File Extension Source and search for information on the extension. Sometimes an extension can be used for multiple types of files, however. A useful utility for identifying the file is TrID. TrID will analyze the file based on its contents and, if it can identify it from the contents, return information about the type of file.
An advantage to using TrID over just trying to ascertain the file type from its extension alone is that it can identify a file type even if the wrong extension is used. For instance, under Windows there are security vulnerabilities where you may receive a file with one type of extension that is actually of a type other than is normally represented by that extension. You may think it is safe to double-click on the file to open it based on the given extension, but by doing so may compromise the security of your system, because Windows will execute code in the file based on its actual contents rather than its file extension. If you check a suspect file with TrID first, you can determine if its actual type matches its stated type.
Or, if you have a file with an unknown extension, you can use TrID to identify the file type and then locate an appropriate program to open that file type.
To install TrID, extract the files within the zip file to a directory on your system, e.g. "C:\Program Files\TrID".
TrID does not use a Graphical User Interface (GUI), so you need to run it from a command line. Once you have a command prompt you can type trid [path]<filespec> to analyze a file. The "path" to the file is not needed if the file is placed in the same directory as the trid.exe file. If the path includes spaces, put the "[path]<filespec>" in quotes as below:
C:\Program Files\Utilities\File\TrID<trid "c:\documents and settings\james\my documents\choose-type-bootable-disc.jpg"
TrID/32 - File Identifier v1.56 - (C) 2003-04 By M.Pontello
Collecting data from file: c:\documents and settings\james\my documents\choose-t
ype-bootable-disc.jpg
Definitions found: 1492
Analyzing...
92.3% (.JPG/JPEG) JFIF JPEG Bitmap (12000/1)
7.7% (.MP3) MP3 audio (1000/1)
If TrID can identify the file type with certainty, only one type will be listed. However, if it can't identify it with absolute certainty, it will list probabilities with the most likely types listed first. In the case of the file above, TrID is 92.3% certain the file is a JPEG file, but there is a small possibility that it is an MP3 audio file, so that possibility is listed as well.
If you wish to see the options you can use when running the program, type trid /?. You will then see the following:
TrID/32 - File Identifier v1.56 - (C) 2003-04 By M.Pontello
Usage: TrID [path]<filespec> [/r:nn] [/v] [/?]
Where: <filespec> File to identify/analyze
/r:nn Display the first nn matches (default: 5)
/v Verbose mode - display def name, author, etc.
/q Quiet - don't show filetypes while loading defs
/? This help!
Developer: Marco Pontello
Developer Website:
Marco Pontello's Home Page
Requirements: Windows 98, ME, NT, 2000, XP, 2003
Purchase Information: Free, but developer requests a small donation.
Recommended: Yes
Download Sites:
Created: 2006-12-17