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

CS file extension

Visual C# Source Code File

Developer Files

DAT file extension

Data File

Data Files

DMP file extension

Windows Memory Dump

System Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LUA file extension

Lua Source File

Developer Files

MOBI file extension

Mobipocket eBook

eBook Files

MPG file extension

MPEG Video File

Video Files

PAGES file extension

Pages Document

Text Files

PART file extension

Partially Downloaded File

Misc Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

RA file extension

Real Audio File

Audio Files

TIFF file extension

Tagged Image File Format

Raster Image Files

XML file extension

XML File

Data Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3DS file extension

3D Studio Scene

3D Image Files