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

CFG file extension

Configuration File

Settings Files

COM file extension

DOS Command File

Executable Files

DBF file extension

Database File

Database Files

DEB file extension

Debian Software Package

Compressed Files

FNT file extension

Windows Font File

Font Files

GADGET file extension

Windows Gadget

Executable Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MOV file extension

Apple QuickTime Movie

Video Files

PIF file extension

Program Information File

Executable Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

SYS file extension

Windows System File

System Files

THM file extension

Thumbnail Image File

Raster Image Files

TMP file extension

Temporary File

Backup Files

TORRENT file extension

BitTorrent File

Misc Files

WMV file extension

Windows Media Video File

Video Files