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

ASPX file extension

Active Server Page Extended File

Web Files

CUR file extension

Windows Cursor

System Files

DTD file extension

Document Type Definition File

Developer Files

FNT file extension

Windows Font File

Font Files

KML file extension

Keyhole Markup Language File

GIS Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PAGES file extension

Pages Document

Text Files

PIF file extension

Program Information File

Executable Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PRF file extension

Outlook Profile File

Settings Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

THM file extension

Thumbnail Image File

Raster Image Files

TIFF file extension

Tagged Image File Format

Raster Image Files

WPD file extension

WordPerfect Document

Text Files