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

AVI file extension

Audio Video Interleave File

Video Files

AZW file extension

Amazon Kindle eBook File

eBook Files

BMP file extension

Bitmap Image File

Raster Image Files

C file extension

C/C++ Source Code File

Developer Files

CFG file extension

Configuration File

Settings Files

COM file extension

DOS Command File

Executable Files

FON file extension

Generic Font File

Font Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

PY file extension

Python Script

Developer Files

SITX file extension

StuffIt X Archive

Compressed Files

SYS file extension

Windows System File

System Files

WPS file extension

Microsoft Works Word Processor Document

Text Files

3G2 file extension

3GPP2 Multimedia File

Video Files

3GP file extension

3GPP Multimedia File

Video Files