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

ZIP file extension

Zipped File

Compressed Files

GZ file extension

Gnu Zipped Archive

Compressed Files

AVI file extension

Audio Video Interleave File

Video Files

SYS file extension

Windows System File

System Files

ASPX file extension

Active Server Page Extended File

Web Files

DNG file extension

Digital Negative Image File

Camera Raw Files

PKG file extension

Mac OS X Installer Package

Compressed Files

NES file extension

Nintendo (NES) ROM File

Game Files

SDF file extension

Standard Data File

Data Files

GADGET file extension

Windows Gadget

Executable Files

CAB file extension

Windows Cabinet File

System Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ASP file extension

Active Server Page

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files