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

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

FLA file extension

Adobe Flash Animation

Developer Files

H file extension

C/C++/Objective-C Header File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

JAVA file extension

Java Source Code File

Developer Files

M file extension

Objective-C Implementation File

Developer Files

MDF file extension

Media Disc Image File

Disk Image Files

MOBI file extension

Mobipocket eBook

eBook Files

MP4 file extension

MPEG-4 Video File

Video Files

MPG file extension

MPEG Video File

Video Files

PAGES file extension

Pages Document

Text Files

PDB file extension

Program Database

Database Files

SLN file extension

Visual Studio Solution File

Developer Files

UUE file extension

Uuencoded File

Encoded Files