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

APP file extension

Mac OS X Application

Executable Files

AVI file extension

Audio Video Interleave File

Video Files

CER file extension

Internet Security Certificate

Web Files

CUR file extension

Windows Cursor

System Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KEY file extension

Keynote Presentation

Data Files

LNK file extension

Windows File Shortcut

System Files

MSG file extension

Outlook Mail Message

Text Files

OTF file extension

OpenType Font

Font Files

SWF file extension

Shockwave Flash Movie

Video Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

VB file extension

VBScript File

Executable Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

ZIPX file extension

Extended Zip File

Compressed Files