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

M4V file extension

iTunes Video File

Video Files

CS file extension

Visual C# Source Code File

Developer Files

3DS file extension

3D Studio Scene

3D Image Files

THM file extension

Thumbnail Image File

Raster Image Files

TXT file extension

Plain Text File

Text Files

CSV file extension

Comma Separated Values File

Data Files

DAT file extension

Data File

Data Files

WAV file extension

WAVE Audio File

Audio Files

XML file extension

XML File

Data Files

FNT file extension

Windows Font File

Font Files

DEM file extension

Video Game Demo File

Game Files

7Z file extension

7-Zip Compressed File

Compressed Files

PAGES file extension

Pages Document

Text Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

TTF file extension

TrueType Font

Font Files