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

AIF file extension

Audio Interchange File Format

Audio Files

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

CSS file extension

Cascading Style Sheet

Web Files

FLV file extension

Flash Video File

Video Files

IBOOKS file extension

Multi-Touch iBook

Data Files

M file extension

Objective-C Implementation File

Developer Files

PL file extension

Perl Script

Developer Files

RSS file extension

Rich Site Summary

Web Files

TGA file extension

Targa Graphic

Raster Image Files

TORRENT file extension

BitTorrent File

Misc Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3G2 file extension

3GPP2 Multimedia File

Video Files