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

DLL file extension

Dynamic Link Library

System Files

AVI file extension

Audio Video Interleave File

Video Files

DAT file extension

Data File

Data Files

WSF file extension

Windows Script File

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

VCXPROJ file extension

Visual C++ Project

Developer Files

KMZ file extension

Google Earth Placemark File

GIS Files

ASX file extension

Microsoft ASF Redirector File

Video Files

MP4 file extension

MPEG-4 Video File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

TIF file extension

Tagged Image File

Raster Image Files

XML file extension

XML File

Data Files

TAR file extension

Consolidated Unix File Archive

Data Files

ODT file extension

OpenDocument Text Document

Text Files