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

ASP file extension

Active Server Page

Web Files

CER file extension

Internet Security Certificate

Web Files

CLASS file extension

Java Class File

Developer Files

DNG file extension

Digital Negative Image File

Camera Raw Files

GAM file extension

Saved Game File

Game Files

INI file extension

Windows Initialization File

Settings Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4V file extension

iTunes Video File

Video Files

MSI file extension

Windows Installer Package

Misc Files

PY file extension

Python Script

Developer Files

SRT file extension

SubRip Subtitle File

Video Files

VB file extension

VBScript File

Executable Files

3G2 file extension

3GPP2 Multimedia File

Video Files

3GP file extension

3GPP Multimedia File

Video Files