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

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

CUE file extension

Cue Sheet File

Disk Image Files

3GP file extension

3GPP Multimedia File

Video Files

PKG file extension

Mac OS X Installer Package

Compressed Files

7Z file extension

7-Zip Compressed File

Compressed Files

SITX file extension

StuffIt X Archive

Compressed Files

WMV file extension

Windows Media Video File

Video Files

APP file extension

Mac OS X Application

Executable Files

PPT file extension

PowerPoint Presentation

Data Files

MDB file extension

Microsoft Access Database

Database Files

DLL file extension

Dynamic Link Library

System Files

INI file extension

Windows Initialization File

Settings Files

VCF file extension

vCard File

Data Files

ASPX file extension

Active Server Page Extended File

Web Files

BMP file extension

Bitmap Image File

Raster Image Files