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

RM file extension

Real Media File

Video Files

GADGET file extension

Windows Gadget

Executable Files

PPS file extension

PowerPoint Slide Show

Data Files

RSS file extension

Rich Site Summary

Web Files

SITX file extension

StuffIt X Archive

Compressed Files

VOB file extension

DVD Video Object File

Video Files

M file extension

Objective-C Implementation File

Developer Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

DDS file extension

DirectDraw Surface

Raster Image Files

JAVA file extension

Java Source Code File

Developer Files

PCT file extension

Picture File

Layout Files

APP file extension

Mac OS X Application

Executable Files

7Z file extension

7-Zip Compressed File

Compressed Files

TTF file extension

TrueType Font

Font Files

CSR file extension

Certificate Signing Request File

Web Files