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

CSS file extension

Cascading Style Sheet

Web Files

TTF file extension

TrueType Font

Font Files

TORRENT file extension

BitTorrent File

Misc Files

7Z file extension

7-Zip Compressed File

Compressed Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

SWF file extension

Shockwave Flash Movie

Video Files

COM file extension

DOS Command File

Executable Files

SRT file extension

SubRip Subtitle File

Video Files

AIF file extension

Audio Interchange File Format

Audio Files

CLASS file extension

Java Class File

Developer Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

INDD file extension

Adobe InDesign Document

Layout Files

CS file extension

Visual C# Source Code File

Developer Files

PCT file extension

Picture File

Layout Files

MAX file extension

3ds Max Scene File

3D Image Files