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

APP file extension

Mac OS X Application

Executable Files

COM file extension

DOS Command File

Executable Files

CPP file extension

C++ Source Code File

Developer Files

DBF file extension

Database File

Database Files

DDS file extension

DirectDraw Surface

Raster Image Files

DRV file extension

Device Driver

System Files

GADGET file extension

Windows Gadget

Executable Files

GBR file extension

Gerber File

Data Files

IFF file extension

Interchange File Format

Audio Files

KEY file extension

Keynote Presentation

Data Files

MDB file extension

Microsoft Access Database

Database Files

RM file extension

Real Media File

Video Files

SLN file extension

Visual Studio Solution File

Developer Files

WSF file extension

Windows Script File

Executable Files

3GP file extension

3GPP Multimedia File

Video Files