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

ASX file extension

Microsoft ASF Redirector File

Video Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DOC file extension

Microsoft Word Document

Text Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

INI file extension

Windows Initialization File

Settings Files

KEY file extension

Keynote Presentation

Data Files

MPA file extension

MPEG-2 Audio File

Audio Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PL file extension

Perl Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

SDF file extension

Standard Data File

Data Files

SH file extension

Bash Shell Script

Developer Files

TARGZ file extension

Compressed Tarball File

Compressed Files

WPD file extension

WordPerfect Document

Text Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files