File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

COM file extension

DOS Command File

Executable Files

DOC# file extension

Microsoft Word Document

Text Files

HTML file extension

Hypertext Markup Language File

Web Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

ISO file extension

Disc Image File

Disk Image Files

JSP file extension

Java Server Page

Web Files

MOV file extension

Apple QuickTime Movie

Video Files

PIF file extension

Program Information File

Executable Files

PRF file extension

Outlook Profile File

Settings Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

WMA file extension

Windows Media Audio File

Audio Files

3GP file extension

3GPP Multimedia File

Video Files