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

APP file extension

Mac OS X Application

Executable Files

ASX file extension

Microsoft ASF Redirector File

Video Files

BAK file extension

Backup File

Backup Files

BAT file extension

DOS Batch File

Executable Files

CAB file extension

Windows Cabinet File

System Files

CPP file extension

C++ Source Code File

Developer Files

DB file extension

Database File

Database Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

INDD file extension

Adobe InDesign Document

Layout Files

PAGES file extension

Pages Document

Text Files

RA file extension

Real Audio File

Audio Files

TIF file extension

Tagged Image File

Raster Image Files

TXT file extension

Plain Text File

Text Files

VOB file extension

DVD Video Object File

Video Files

ZIPX file extension

Extended Zip File

Compressed Files