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

INI file extension

Windows Initialization File

Settings Files

LNK file extension

Windows File Shortcut

System Files

ROM file extension

N64 Game ROM File

Game Files

ACCDB file extension

Access 2007 Database File

Database Files

PDB file extension

Program Database

Database Files

CLASS file extension

Java Class File

Developer Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

EPUB file extension

Open eBook File

eBook Files

7Z file extension

7-Zip Compressed File

Compressed Files

DDS file extension

DirectDraw Surface

Raster Image Files

PRF file extension

Outlook Profile File

Settings Files

TGA file extension

Targa Graphic

Raster Image Files

DWG file extension

AutoCAD Drawing Database File

CAD Files

RA file extension

Real Audio File

Audio Files

ICNS file extension

Mac OS X Icon Resource File

System Files