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

ASX file extension

Microsoft ASF Redirector File

Video Files

BAK file extension

Backup File

Backup Files

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CFG file extension

Configuration File

Settings Files

GBR file extension

Gerber File

Data Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

ICS file extension

iCalendar File

Misc Files

KEY file extension

Keynote Presentation

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

PART file extension

Partially Downloaded File

Misc Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files