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

AIF file extension

Audio Interchange File Format

Audio Files

CFG file extension

Configuration File

Settings Files

CGI file extension

Common Gateway Interface Script

Executable Files

CLASS file extension

Java Class File

Developer Files

DBF file extension

Database File

Database Files

DOC# file extension

Microsoft Word Document

Text Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ICO file extension

Icon File

System Files

MDF file extension

Media Disc Image File

Disk Image Files

PDB file extension

Program Database

Database Files

RA file extension

Real Audio File

Audio Files

RM file extension

Real Media File

Video Files

RTF file extension

Rich Text Format File

Text Files

SYS file extension

Windows System File

System Files

3DS file extension

3D Studio Scene

3D Image Files