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

CAB file extension

Windows Cabinet File

System Files

CSS file extension

Cascading Style Sheet

Web Files

DRV file extension

Device Driver

System Files

EXE file extension

Windows Executable File

Executable Files

GED file extension

GEDCOM Genealogy Data File

Data Files

JS file extension

JavaScript File

Web Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MDF file extension

Media Disc Image File

Disk Image Files

PIF file extension

Program Information File

Executable Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

SAV file extension

Saved Game

Game Files

SLN file extension

Visual Studio Solution File

Developer Files

WPD file extension

WordPerfect Document

Text Files