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

MPG file extension

MPEG Video File

Video Files

SLN file extension

Visual Studio Solution File

Developer Files

DRV file extension

Device Driver

System Files

RA file extension

Real Audio File

Audio Files

7Z file extension

7-Zip Compressed File

Compressed Files

CFM file extension

ColdFusion Markup File

Web Files

DXF file extension

Drawing Exchange Format File

CAD Files

DLL file extension

Dynamic Link Library

System Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

ISO file extension

Disc Image File

Disk Image Files

RTF file extension

Rich Text Format File

Text Files

KEY file extension

Keynote Presentation

Data Files

3GP file extension

3GPP Multimedia File

Video Files

PY file extension

Python Script

Developer Files