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

ASPX file extension

Active Server Page Extended File

Web Files

CPL file extension

Windows Control Panel Item

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

DOC# file extension

Microsoft Word Document

Text Files

HTML file extension

Hypertext Markup Language File

Web Files

INI file extension

Windows Initialization File

Settings Files

JS file extension

JavaScript File

Web Files

LOG file extension

Log File

Text Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RM file extension

Real Media File

Video Files

RTF file extension

Rich Text Format File

Text Files

TAR file extension

Consolidated Unix File Archive

Data Files

TOAST file extension

Toast Disc Image

Disk Image Files

WMA file extension

Windows Media Audio File

Audio Files