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

FNT file extension

Windows Font File

Font Files

SDF file extension

Standard Data File

Data Files

GBR file extension

Gerber File

Data Files

7Z file extension

7-Zip Compressed File

Compressed Files

CBR file extension

Comic Book RAR Archive

Compressed Files

COM file extension

DOS Command File

Executable Files

ASF file extension

Advanced Systems Format File

Video Files

LOG file extension

Log File

Text Files

MPG file extension

MPEG Video File

Video Files

ROM file extension

N64 Game ROM File

Game Files

WMV file extension

Windows Media Video File

Video Files

CAB file extension

Windows Cabinet File

System Files

KML file extension

Keyhole Markup Language File

GIS Files

DOC file extension

Microsoft Word Document

Text Files

XML file extension

XML File

Data Files