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

DLL file extension

Dynamic Link Library

System Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

HTML file extension

Hypertext Markup Language File

Web Files

ISO file extension

Disc Image File

Disk Image Files

KML file extension

Keyhole Markup Language File

GIS Files

LOG file extension

Log File

Text Files

M4A file extension

MPEG-4 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PRF file extension

Outlook Profile File

Settings Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

WSF file extension

Windows Script File

Executable Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3DS file extension

3D Studio Scene

3D Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files