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

CLASS file extension

Java Class File

Developer Files

CPL file extension

Windows Control Panel Item

System Files

CSS file extension

Cascading Style Sheet

Web Files

DOC# file extension

Microsoft Word Document

Text Files

DXF file extension

Drawing Exchange Format File

CAD Files

GZ file extension

Gnu Zipped Archive

Compressed Files

H file extension

C/C++/Objective-C Header File

Developer Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PNG file extension

Portable Network Graphic

Raster Image Files

RPM file extension

Red Hat Package Manager File

Compressed Files

SITX file extension

StuffIt X Archive

Compressed Files

TARGZ file extension

Compressed Tarball File

Compressed Files

VCF file extension

vCard File

Data Files

VCXPROJ file extension

Visual C++ Project

Developer Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files