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

ASF file extension

Advanced Systems Format File

Video Files

GAM file extension

Saved Game File

Game Files

IBOOKS file extension

Multi-Touch iBook

Data Files

INDD file extension

Adobe InDesign Document

Layout Files

KEY file extension

Keynote Presentation

Data Files

MDF file extension

Media Disc Image File

Disk Image Files

MOBI file extension

Mobipocket eBook

eBook Files

ODT file extension

OpenDocument Text Document

Text Files

RTF file extension

Rich Text Format File

Text Files

SAV file extension

Saved Game

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

SWF file extension

Shockwave Flash Movie

Video Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

YUV file extension

YUV Encoded Image File

Raster Image Files