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

APP file extension

Mac OS X Application

Executable Files

ASF file extension

Advanced Systems Format File

Video Files

DRV file extension

Device Driver

System Files

GAM file extension

Saved Game File

Game Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

IFF file extension

Interchange File Format

Audio Files

JS file extension

JavaScript File

Web Files

MP4 file extension

MPEG-4 Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

NES file extension

Nintendo (NES) ROM File

Game Files

RA file extension

Real Audio File

Audio Files

WPD file extension

WordPerfect Document

Text Files

WSF file extension

Windows Script File

Executable Files

XLR file extension

Works Spreadsheet

Spreadsheet Files