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

AIF file extension

Audio Interchange File Format

Audio Files

COM file extension

DOS Command File

Executable Files

CSS file extension

Cascading Style Sheet

Web Files

CSV file extension

Comma Separated Values File

Data Files

CUR file extension

Windows Cursor

System Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DOC file extension

Microsoft Word Document

Text Files

GADGET file extension

Windows Gadget

Executable Files

JS file extension

JavaScript File

Web Files

NES file extension

Nintendo (NES) ROM File

Game Files

OTF file extension

OpenType Font

Font Files

SAV file extension

Saved Game

Game Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TMP file extension

Temporary File

Backup Files

WSF file extension

Windows Script File

Executable Files