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

LNK file extension

Windows File Shortcut

System Files

3DM file extension

Rhino 3D Model

3D Image Files

CAB file extension

Windows Cabinet File

System Files

PAGES file extension

Pages Document

Text Files

MOBI file extension

Mobipocket eBook

eBook Files

MSG file extension

Outlook Mail Message

Text Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

FON file extension

Generic Font File

Font Files

LUA file extension

Lua Source File

Developer Files

HQX file extension

BinHex 4.0 Encoded File

Encoded Files

ACCDB file extension

Access 2007 Database File

Database Files

ASP file extension

Active Server Page

Web Files

7Z file extension

7-Zip Compressed File

Compressed Files

KMZ file extension

Google Earth Placemark File

GIS Files

PL file extension

Perl Script

Developer Files