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

C file extension

C/C++ Source Code File

Developer Files

CAB file extension

Windows Cabinet File

System Files

CGI file extension

Common Gateway Interface Script

Executable Files

CPP file extension

C++ Source Code File

Developer Files

CS file extension

Visual C# Source Code File

Developer Files

DAT file extension

Data File

Data Files

ICNS file extension

Mac OS X Icon Resource File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MPA file extension

MPEG-2 Audio File

Audio Files

PRF file extension

Outlook Profile File

Settings Files

SAV file extension

Saved Game

Game Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

3DS file extension

3D Studio Scene

3D Image Files

3GP file extension

3GPP Multimedia File

Video Files