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

DEM file extension

Video Game Demo File

Game Files

DLL file extension

Dynamic Link Library

System Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

INI file extension

Windows Initialization File

Settings Files

KMZ file extension

Google Earth Placemark File

GIS Files

PAGES file extension

Pages Document

Text Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RM file extension

Real Media File

Video Files

ROM file extension

N64 Game ROM File

Game Files

RPM file extension

Red Hat Package Manager File

Compressed Files

TXT file extension

Plain Text File

Text Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files