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

AI file extension

Adobe Illustrator File

Vector Image Files

CER file extension

Internet Security Certificate

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

CSV file extension

Comma Separated Values File

Data Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

DXF file extension

Drawing Exchange Format File

CAD Files

GADGET file extension

Windows Gadget

Executable Files

HTML file extension

Hypertext Markup Language File

Web Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

NES file extension

Nintendo (NES) ROM File

Game Files

PCT file extension

Picture File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

YUV file extension

YUV Encoded Image File

Raster Image Files