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

CLASS file extension

Java Class File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

DTD file extension

Document Type Definition File

Developer Files

EXE file extension

Windows Executable File

Executable Files

FLV file extension

Flash Video File

Video Files

ICNS file extension

Mac OS X Icon Resource File

System Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

INI file extension

Windows Initialization File

Settings Files

MP3 file extension

MP3 Audio File

Audio Files

PS file extension

PostScript File

Vector Image Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TTF file extension

TrueType Font

Font Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WSF file extension

Windows Script File

Executable Files