Filenames and File Extensions

file extensions
Welcome to our filename and file extension guide.

This section is designed to give you an idea of what file extensions are and what they mean. We have also included a list of file extensions that are in common use along with their description.
The name of a file is made up of two parts, the actual name of the file, and what is called the file extension (suffix).

The file extension is what the computer uses to identify what type of file it is and subsequently which software application is associated with the file. You will never normally have to assign file extensions manually as your software application will usually do it for you, but it is handy to know what they mean.

First of all an example :


In this example anyfile is the filename and txt is the file extension (suffix). Notice that the filename and file extension are separated by way of a full stop (period).

List of common file extensions and their meanings:

Extension Description
anyfile.avi This is a video format.
anyfile.bat This is called a batch file and normally contains MS-DOS commands.
anyfile.bmp This is called a bitmap file, it is a graphical image format.
anyfile.dll DLL refers to a type of file which contains common data which can be shared by different programs on the same platform.
anyfile.doc This is a Microsoft Word document file.
anyfile.xls This is a Microsoft Excel file.
anyfile.mdb This is a Microsoft Access database file. This is a movie file used by Apple Quicktime®.
anyfile.gif This is another graphical image format typically used on the Internet.
anyfile.ini This type of file contains information about the initiation of your system - Never manipulate these files.
anyfile.jpg A graphical image format.
anyfile.sys This is a system file used by the system - Never manipulate these files
anyfile.txt This type of file contains text such as that created with the notepad program in windows.
anyfile.wav This is a wave file, it is an audio file such as the one that plays when you start windows.
anyfile.pdf A file used by Adobe Acrobat software.
anyfile.mp3 This is a compressed audio file.

These are a few examples of file extensions. Each software package you use on your PC whether it is your word processor, graphics package, spreadsheet or any other program will usually utilise their own particular file extension.

When you are choosing a filename avoid using any special characters, including:

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Use alphanumeric characters only, for example:


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