Filenames and 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.

Before you follow this tutorial you must read the terms of our disclaimer.

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 alter file extensions manually, your software application will usually do it for you, but it is handy to know what they mean.

First of all an example :

anyfile.txt

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.

List of common file extensions and their meanings:

Extension	Description
anyfile.avi	This is a video format, click here for more info
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, click here for more info
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.
anyfile.mov	This is a movie file used by Apple Quicktime®.
anyfile.gif	This is another graphical image format typically used on the internet, click here for more info.
anyfile.ini	This type of file contains information about the initiation of your system - Never manipulate these files.
anyfile.jpg	A graphical image format, click here for more info.
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, click here for more info.
anyfile.pdf	A file used by Adobe Acrobat Software, click here for more info.
anyfile.mp3	This is a compressed audio file, click here for more info

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:

! " # $ % & / ( ) = ? '{ } [ ] § @ , . ; : \ | < >

Use alphanumeric characters only, for example:

1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ