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

AIF file extension

Audio Interchange File Format

Audio Files

AVI file extension

Audio Video Interleave File

Video Files

BAK file extension

Backup File

Backup Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CS file extension

Visual C# Source Code File

Developer Files

DTD file extension

Document Type Definition File

Developer Files

FON file extension

Generic Font File

Font Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KMZ file extension

Google Earth Placemark File

GIS Files

MDF file extension

Media Disc Image File

Disk Image Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PRF file extension

Outlook Profile File

Settings Files

PS file extension

PostScript File

Vector Image Files

SLN file extension

Visual Studio Solution File

Developer Files

VOB file extension

DVD Video Object File

Video Files