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

ASX file extension

Microsoft ASF Redirector File

Video Files

CAB file extension

Windows Cabinet File

System Files

CFG file extension

Configuration File

Settings Files

CPL file extension

Windows Control Panel Item

System Files

DAT file extension

Data File

Data Files

DOC# file extension

Microsoft Word Document

Text Files

ICO file extension

Icon File

System Files

MDF file extension

Media Disc Image File

Disk Image Files

NES file extension

Nintendo (NES) ROM File

Game Files

PIF file extension

Program Information File

Executable Files

SITX file extension

StuffIt X Archive

Compressed Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TIF file extension

Tagged Image File

Raster Image Files

TMP file extension

Temporary File

Backup Files

XLR file extension

Works Spreadsheet

Spreadsheet Files