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

CFG file extension

Configuration File

Settings Files

CPP file extension

C++ Source Code File

Developer Files

DDS file extension

DirectDraw Surface

Raster Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

FNT file extension

Windows Font File

Font Files

ICO file extension

Icon File

System Files

INI file extension

Windows Initialization File

Settings Files

JS file extension

JavaScript File

Web Files

PCT file extension

Picture File

Layout Files

PIF file extension

Program Information File

Executable Files

PPT file extension

PowerPoint Presentation

Data Files

PS file extension

PostScript File

Vector Image Files

UUE file extension

Uuencoded File

Encoded Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

YUV file extension

YUV Encoded Image File

Raster Image Files