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

C file extension

C/C++ Source Code File

Developer Files

CER file extension

Internet Security Certificate

Web Files

CLASS file extension

Java Class File

Developer Files

CSR file extension

Certificate Signing Request File

Web Files

DAT file extension

Data File

Data Files

DEM file extension

Video Game Demo File

Game Files

FLA file extension

Adobe Flash Animation

Developer Files

INI file extension

Windows Initialization File

Settings Files

JPG file extension

JPEG Image

Raster Image Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PAGES file extension

Pages Document

Text Files

PPS file extension

PowerPoint Slide Show

Data Files

SWF file extension

Shockwave Flash Movie

Video Files

TXT file extension

Plain Text File

Text Files

WSF file extension

Windows Script File

Executable Files