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

DAT file extension

Data File

Data Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

MSG file extension

Outlook Mail Message

Text Files

PPT file extension

PowerPoint Presentation

Data Files

PNG file extension

Portable Network Graphic

Raster Image Files

7Z file extension

7-Zip Compressed File

Compressed Files

PKG file extension

Mac OS X Installer Package

Compressed Files

KMZ file extension

Google Earth Placemark File

GIS Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

CS file extension

Visual C# Source Code File

Developer Files

H file extension

C/C++/Objective-C Header File

Developer Files

ASF file extension

Advanced Systems Format File

Video Files

DLL file extension

Dynamic Link Library

System Files

SYS file extension

Windows System File

System Files

FON file extension

Generic Font File

Font Files