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

CS file extension

Visual C# Source Code File

Developer Files

CUE file extension

Cue Sheet File

Disk Image Files

CUR file extension

Windows Cursor

System Files

DDS file extension

DirectDraw Surface

Raster Image Files

DEM file extension

Video Game Demo File

Game Files

JAR file extension

Java Archive File

Executable Files

KMZ file extension

Google Earth Placemark File

GIS Files

MID file extension

MIDI File

Audio Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PRF file extension

Outlook Profile File

Settings Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLR file extension

Works Spreadsheet

Spreadsheet Files