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

DLL file extension

Dynamic Link Library

System Files

JPG file extension

JPEG Image

Raster Image Files

LUA file extension

Lua Source File

Developer Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PS file extension

PostScript File

Vector Image Files

RM file extension

Real Media File

Video Files

RTF file extension

Rich Text Format File

Text Files

TOAST file extension

Toast Disc Image

Disk Image Files

TXT file extension

Plain Text File

Text Files

XCODEPROJ file extension

Xcode Project

Developer Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3DS file extension

3D Studio Scene

3D Image Files