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

7Z file extension

7-Zip Compressed File

Compressed Files

BIN file extension

Binary Disc Image

Disk Image Files

3DS file extension

3D Studio Scene

3D Image Files

MPA file extension

MPEG-2 Audio File

Audio Files

PCT file extension

Picture File

Layout Files

ICO file extension

Icon File

System Files

CGI file extension

Common Gateway Interface Script

Executable Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

MOV file extension

Apple QuickTime Movie

Video Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

NES file extension

Nintendo (NES) ROM File

Game Files

CPP file extension

C++ Source Code File

Developer Files

ASPX file extension

Active Server Page Extended File

Web Files

CBR file extension

Comic Book RAR Archive

Compressed Files

M file extension

Objective-C Implementation File

Developer Files