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

3DM file extension

Rhino 3D Model

3D Image Files

ZIPX file extension

Extended Zip File

Compressed Files

H file extension

C/C++/Objective-C Header File

Developer Files

7Z file extension

7-Zip Compressed File

Compressed Files

ACCDB file extension

Access 2007 Database File

Database Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

WMV file extension

Windows Media Video File

Video Files

MOV file extension

Apple QuickTime Movie

Video Files

DDS file extension

DirectDraw Surface

Raster Image Files

DEB file extension

Debian Software Package

Compressed Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

VCF file extension

vCard File

Data Files

MSG file extension

Outlook Mail Message

Text Files

PIF file extension

Program Information File

Executable Files

ICNS file extension

Mac OS X Icon Resource File

System Files