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

BAT file extension

DOS Batch File

Executable Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GED file extension

GEDCOM Genealogy Data File

Data Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

KEY file extension

Keynote Presentation

Data Files

NES file extension

Nintendo (NES) ROM File

Game Files

PART file extension

Partially Downloaded File

Misc Files

PRF file extension

Outlook Profile File

Settings Files

PS file extension

PostScript File

Vector Image Files

SITX file extension

StuffIt X Archive

Compressed Files

SLN file extension

Visual Studio Solution File

Developer Files

THM file extension

Thumbnail Image File

Raster Image Files

3GP file extension

3GPP Multimedia File

Video Files