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

CGI file extension

Common Gateway Interface Script

Executable Files

CPL file extension

Windows Control Panel Item

System Files

DEM file extension

Video Game Demo File

Game Files

DMP file extension

Windows Memory Dump

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DRV file extension

Device Driver

System Files

EPUB file extension

Open eBook File

eBook Files

ICNS file extension

Mac OS X Icon Resource File

System Files

IFF file extension

Interchange File Format

Audio Files

KEY file extension

Keynote Presentation

Data Files

MID file extension

MIDI File

Audio Files

PCT file extension

Picture File

Layout Files

PPS file extension

PowerPoint Slide Show

Data Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TTF file extension

TrueType Font

Font Files