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

COM file extension

DOS Command File

Executable Files

CSV file extension

Comma Separated Values File

Data Files

DMP file extension

Windows Memory Dump

System Files

DXF file extension

Drawing Exchange Format File

CAD Files

EXE file extension

Windows Executable File

Executable Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

PCT file extension

Picture File

Layout Files

PHP file extension

PHP Source Code File

Web Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RTF file extension

Rich Text Format File

Text Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WMA file extension

Windows Media Audio File

Audio Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files