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

ASF file extension

Advanced Systems Format File

Video Files

ASP file extension

Active Server Page

Web Files

DLL file extension

Dynamic Link Library

System Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GPX file extension

GPS Exchange File

GIS Files

IFF file extension

Interchange File Format

Audio Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MOV file extension

Apple QuickTime Movie

Video Files

MSG file extension

Outlook Mail Message

Text Files

SQL file extension

Structured Query Language Data File

Database Files

TGA file extension

Targa Graphic

Raster Image Files

TXT file extension

Plain Text File

Text Files

WPD file extension

WordPerfect Document

Text Files

ZIPX file extension

Extended Zip File

Compressed Files

3DM file extension

Rhino 3D Model

3D Image Files