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

APP file extension

Mac OS X Application

Executable Files

CSS file extension

Cascading Style Sheet

Web Files

M4A file extension

MPEG-4 Audio File

Audio Files

SLN file extension

Visual Studio Solution File

Developer Files

TOAST file extension

Toast Disc Image

Disk Image Files

CUR file extension

Windows Cursor

System Files

7Z file extension

7-Zip Compressed File

Compressed Files

VOB file extension

DVD Video Object File

Video Files

BMP file extension

Bitmap Image File

Raster Image Files

PRF file extension

Outlook Profile File

Settings Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAR file extension

Java Archive File

Executable Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

ROM file extension

N64 Game ROM File

Game Files

CUE file extension

Cue Sheet File

Disk Image Files