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

CUE file extension

Cue Sheet File

Disk Image Files

DLL file extension

Dynamic Link Library

System Files

DRV file extension

Device Driver

System Files

GPX file extension

GPS Exchange File

GIS Files

HTML file extension

Hypertext Markup Language File

Web Files

ICO file extension

Icon File

System Files

IFF file extension

Interchange File Format

Audio Files

INI file extension

Windows Initialization File

Settings Files

KEY file extension

Keynote Presentation

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

MDF file extension

Media Disc Image File

Disk Image Files

PHP file extension

PHP Source Code File

Web Files

RA file extension

Real Audio File

Audio Files

SQL file extension

Structured Query Language Data File

Database Files