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

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

VOB file extension

DVD Video Object File

Video Files

HTML file extension

Hypertext Markup Language File

Web Files

DB file extension

Database File

Database Files

MSG file extension

Outlook Mail Message

Text Files

THM file extension

Thumbnail Image File

Raster Image Files

3DM file extension

Rhino 3D Model

3D Image Files

COM file extension

DOS Command File

Executable Files

LOG file extension

Log File

Text Files

FON file extension

Generic Font File

Font Files

CFM file extension

ColdFusion Markup File

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

PNG file extension

Portable Network Graphic

Raster Image Files

MPG file extension

MPEG Video File

Video Files

SYS file extension

Windows System File

System Files