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

AI file extension

Adobe Illustrator File

Vector Image Files

ASF file extension

Advanced Systems Format File

Video Files

CAB file extension

Windows Cabinet File

System Files

CFM file extension

ColdFusion Markup File

Web Files

CS file extension

Visual C# Source Code File

Developer Files

DNG file extension

Digital Negative Image File

Camera Raw Files

M4A file extension

MPEG-4 Audio File

Audio Files

MP4 file extension

MPEG-4 Video File

Video Files

ODT file extension

OpenDocument Text Document

Text Files

RTF file extension

Rich Text Format File

Text Files

SITX file extension

StuffIt X Archive

Compressed Files

SYS file extension

Windows System File

System Files

VCXPROJ file extension

Visual C++ Project

Developer Files

WAV file extension

WAVE Audio File

Audio Files

ZIPX file extension

Extended Zip File

Compressed Files