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

ROM file extension

N64 Game ROM File

Game Files

AZW file extension

Amazon Kindle eBook File

eBook Files

EXE file extension

Windows Executable File

Executable Files

KML file extension

Keyhole Markup Language File

GIS Files

7Z file extension

7-Zip Compressed File

Compressed Files

PHP file extension

PHP Source Code File

Web Files

DOC# file extension

Microsoft Word Document

Text Files

ICS file extension

iCalendar File

Misc Files

JSP file extension

Java Server Page

Web Files

MP4 file extension

MPEG-4 Video File

Video Files

RM file extension

Real Media File

Video Files

TORRENT file extension

BitTorrent File

Misc Files

ICNS file extension

Mac OS X Icon Resource File

System Files

PKG file extension

Mac OS X Installer Package

Compressed Files

WPS file extension

Microsoft Works Word Processor Document

Text Files