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

CFG file extension

Configuration File

Settings Files

CGI file extension

Common Gateway Interface Script

Executable Files

DOC file extension

Microsoft Word Document

Text Files

HTM file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

IFF file extension

Interchange File Format

Audio Files

INDD file extension

Adobe InDesign Document

Layout Files

JAVA file extension

Java Source Code File

Developer Files

MOV file extension

Apple QuickTime Movie

Video Files

MP4 file extension

MPEG-4 Video File

Video Files

NES file extension

Nintendo (NES) ROM File

Game Files

PPT file extension

PowerPoint Presentation

Data Files

PSPIMAGE file extension

PaintShop Pro Image

Raster Image Files

TAR file extension

Consolidated Unix File Archive

Data Files

ZIPX file extension

Extended Zip File

Compressed Files