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

AZW file extension

Amazon Kindle eBook File

eBook Files

BAK file extension

Backup File

Backup Files

CGI file extension

Common Gateway Interface Script

Executable Files

COM file extension

DOS Command File

Executable Files

DAT file extension

Data File

Data Files

EPUB file extension

Open eBook File

eBook Files

JS file extension

JavaScript File

Web Files

PAGES file extension

Pages Document

Text Files

PRF file extension

Outlook Profile File

Settings Files

RM file extension

Real Media File

Video Files

RSS file extension

Rich Site Summary

Web Files

TGA file extension

Targa Graphic

Raster Image Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

XCODEPROJ file extension

Xcode Project

Developer Files

3GP file extension

3GPP Multimedia File

Video Files