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

AI file extension

Adobe Illustrator File

Vector Image Files

ASF file extension

Advanced Systems Format File

Video Files

CFG file extension

Configuration File

Settings Files

CPL file extension

Windows Control Panel Item

System Files

CUE file extension

Cue Sheet File

Disk Image Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

FNT file extension

Windows Font File

Font Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

MP3 file extension

MP3 Audio File

Audio Files

MSI file extension

Windows Installer Package

Misc Files

PDF file extension

Portable Document Format File

Layout Files

PKG file extension

Mac OS X Installer Package

Compressed Files

RSS file extension

Rich Site Summary

Web Files

RTF file extension

Rich Text Format File

Text Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files