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

DOCX file extension

Microsoft Word Open XML Document

Text Files

FLV file extension

Flash Video File

Video Files

GBR file extension

Gerber File

Data Files

GPX file extension

GPS Exchange File

GIS Files

H file extension

C/C++/Objective-C Header File

Developer Files

KEY file extension

Keynote Presentation

Data Files

M3U file extension

Media Playlist File

Audio Files

PHP file extension

PHP Source Code File

Web Files

SRT file extension

SubRip Subtitle File

Video Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TOAST file extension

Toast Disc Image

Disk Image Files

TORRENT file extension

BitTorrent File

Misc Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

3G2 file extension

3GPP2 Multimedia File

Video Files