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

DEM file extension

Video Game Demo File

Game Files

DOC file extension

Microsoft Word Document

Text Files

GADGET file extension

Windows Gadget

Executable Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

INDD file extension

Adobe InDesign Document

Layout Files

JPG file extension

JPEG Image

Raster Image Files

PHP file extension

PHP Source Code File

Web Files

PPS file extension

PowerPoint Slide Show

Data Files

PY file extension

Python Script

Developer Files

RTF file extension

Rich Text Format File

Text Files

TAR file extension

Consolidated Unix File Archive

Data Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

3GP file extension

3GPP Multimedia File

Video Files