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

CER file extension

Internet Security Certificate

Web Files

CS file extension

Visual C# Source Code File

Developer Files

FNT file extension

Windows Font File

Font Files

FON file extension

Generic Font File

Font Files

GPX file extension

GPS Exchange File

GIS Files

KMZ file extension

Google Earth Placemark File

GIS Files

LOG file extension

Log File

Text Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PCT file extension

Picture File

Layout Files

PHP file extension

PHP Source Code File

Web Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

SYS file extension

Windows System File

System Files

VOB file extension

DVD Video Object File

Video Files

WAV file extension

WAVE Audio File

Audio Files

WMA file extension

Windows Media Audio File

Audio Files