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

CBR file extension

Comic Book RAR Archive

Compressed Files

CFG file extension

Configuration File

Settings Files

CS file extension

Visual C# Source Code File

Developer Files

DEM file extension

Video Game Demo File

Game Files

INI file extension

Windows Initialization File

Settings Files

KML file extension

Keyhole Markup Language File

GIS Files

MAX file extension

3ds Max Scene File

3D Image Files

MOBI file extension

Mobipocket eBook

eBook Files

PHP file extension

PHP Source Code File

Web Files

SAV file extension

Saved Game

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

TOAST file extension

Toast Disc Image

Disk Image Files

VCF file extension

vCard File

Data Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files