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

CFG file extension

Configuration File

Settings Files

CS file extension

Visual C# Source Code File

Developer Files

DOC file extension

Microsoft Word Document

Text Files

FLV file extension

Flash Video File

Video Files

GADGET file extension

Windows Gadget

Executable Files

GBR file extension

Gerber File

Data Files

H file extension

C/C++/Objective-C Header File

Developer Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

LNK file extension

Windows File Shortcut

System Files

LOG file extension

Log File

Text Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

RM file extension

Real Media File

Video Files

SRT file extension

SubRip Subtitle File

Video Files

VCD file extension

Virtual CD

Disk Image Files