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

CFM file extension

ColdFusion Markup File

Web Files

CGI file extension

Common Gateway Interface Script

Executable Files

CPP file extension

C++ Source Code File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

CUE file extension

Cue Sheet File

Disk Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DMP file extension

Windows Memory Dump

System Files

H file extension

C/C++/Objective-C Header File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

IFF file extension

Interchange File Format

Audio Files

LUA file extension

Lua Source File

Developer Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

THM file extension

Thumbnail Image File

Raster Image Files

UUE file extension

Uuencoded File

Encoded Files

VCXPROJ file extension

Visual C++ Project

Developer Files