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

AVI file extension

Audio Video Interleave File

Video Files

FLV file extension

Flash Video File

Video Files

FNT file extension

Windows Font File

Font Files

GED file extension

GEDCOM Genealogy Data File

Data Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JSP file extension

Java Server Page

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

ODT file extension

OpenDocument Text Document

Text Files

PHP file extension

PHP Source Code File

Web Files

RA file extension

Real Audio File

Audio Files

RTF file extension

Rich Text Format File

Text Files

SLN file extension

Visual Studio Solution File

Developer Files

SYS file extension

Windows System File

System Files

XCODEPROJ file extension

Xcode Project

Developer Files

XML file extension

XML File

Data Files