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

ASF file extension

Advanced Systems Format File

Video Files

COM file extension

DOS Command File

Executable Files

CRX file extension

Chrome Extension

Plugin Files

DEM file extension

Video Game Demo File

Game Files

ISO file extension

Disc Image File

Disk Image Files

JS file extension

JavaScript File

Web Files

JSP file extension

Java Server Page

Web Files

KEY file extension

Keynote Presentation

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PPS file extension

PowerPoint Slide Show

Data Files

PPT file extension

PowerPoint Presentation

Data Files

PRF file extension

Outlook Profile File

Settings Files

SDF file extension

Standard Data File

Data Files

3G2 file extension

3GPP2 Multimedia File

Video Files