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

BAK file extension

Backup File

Backup Files

RSS file extension

Rich Site Summary

Web Files

GPX file extension

GPS Exchange File

GIS Files

CPP file extension

C++ Source Code File

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

C file extension

C/C++ Source Code File

Developer Files

CFG file extension

Configuration File

Settings Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

THM file extension

Thumbnail Image File

Raster Image Files

ROM file extension

N64 Game ROM File

Game Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

FNT file extension

Windows Font File

Font Files

XML file extension

XML File

Data Files

3DS file extension

3D Studio Scene

3D Image Files

TORRENT file extension

BitTorrent File

Misc Files