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

DEB file extension

Debian Software Package

Compressed Files

DMP file extension

Windows Memory Dump

System Files

DOC file extension

Microsoft Word Document

Text Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAVA file extension

Java Source Code File

Developer Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LUA file extension

Lua Source File

Developer Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

SDF file extension

Standard Data File

Data Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WMV file extension

Windows Media Video File

Video Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

XML file extension

XML File

Data Files

3DS file extension

3D Studio Scene

3D Image Files