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

CPL file extension

Windows Control Panel Item

System Files

DEB file extension

Debian Software Package

Compressed Files

DXF file extension

Drawing Exchange Format File

CAD Files

INDD file extension

Adobe InDesign Document

Layout Files

KEY file extension

Keynote Presentation

Data Files

LNK file extension

Windows File Shortcut

System Files

M4A file extension

MPEG-4 Audio File

Audio Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

SRT file extension

SubRip Subtitle File

Video Files

TEX file extension

LaTeX Source Document

Text Files

TTF file extension

TrueType Font

Font Files

WPD file extension

WordPerfect Document

Text Files

XCODEPROJ file extension

Xcode Project

Developer Files

ZIP file extension

Zipped File

Compressed Files