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

ASPX file extension

Active Server Page Extended File

Web Files

BMP file extension

Bitmap Image File

Raster Image Files

CAB file extension

Windows Cabinet File

System Files

CGI file extension

Common Gateway Interface Script

Executable Files

CS file extension

Visual C# Source Code File

Developer Files

DDS file extension

DirectDraw Surface

Raster Image Files

GAM file extension

Saved Game File

Game Files

HTM file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

LNK file extension

Windows File Shortcut

System Files

NES file extension

Nintendo (NES) ROM File

Game Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

ROM file extension

N64 Game ROM File

Game Files

TGA file extension

Targa Graphic

Raster Image Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files