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

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

GADGET file extension

Windows Gadget

Executable Files

GPX file extension

GPS Exchange File

GIS Files

KEY file extension

Keynote Presentation

Data Files

MDF file extension

Media Disc Image File

Disk Image Files

MSI file extension

Windows Installer Package

Misc Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

SITX file extension

StuffIt X Archive

Compressed Files

SRT file extension

SubRip Subtitle File

Video Files

THM file extension

Thumbnail Image File

Raster Image Files

VB file extension

VBScript File

Executable Files

VCD file extension

Virtual CD

Disk Image Files

3GP file extension

3GPP Multimedia File

Video Files