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

DEB file extension

Debian Software Package

Compressed Files

PCT file extension

Picture File

Layout Files

ASX file extension

Microsoft ASF Redirector File

Video Files

APP file extension

Mac OS X Application

Executable Files

FLV file extension

Flash Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

WMV file extension

Windows Media Video File

Video Files

PAGES file extension

Pages Document

Text Files

KML file extension

Keyhole Markup Language File

GIS Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

7Z file extension

7-Zip Compressed File

Compressed Files

RTF file extension

Rich Text Format File

Text Files

CFG file extension

Configuration File

Settings Files

GZ file extension

Gnu Zipped Archive

Compressed Files

THM file extension

Thumbnail Image File

Raster Image Files