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

PART file extension

Partially Downloaded File

Misc Files

DXF file extension

Drawing Exchange Format File

CAD Files

FON file extension

Generic Font File

Font Files

ASF file extension

Advanced Systems Format File

Video Files

HTM file extension

Hypertext Markup Language File

Web Files

CLASS file extension

Java Class File

Developer Files

LNK file extension

Windows File Shortcut

System Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

APP file extension

Mac OS X Application

Executable Files

M3U file extension

Media Playlist File

Audio Files

THM file extension

Thumbnail Image File

Raster Image Files

PCT file extension

Picture File

Layout Files

DAT file extension

Data File

Data Files

M4V file extension

iTunes Video File

Video Files

7Z file extension

7-Zip Compressed File

Compressed Files