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

APP file extension

Mac OS X Application

Executable Files

CLASS file extension

Java Class File

Developer Files

CPP file extension

C++ Source Code File

Developer Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CS file extension

Visual C# Source Code File

Developer Files

CUR file extension

Windows Cursor

System Files

DNG file extension

Digital Negative Image File

Camera Raw Files

GZ file extension

Gnu Zipped Archive

Compressed Files

ICO file extension

Icon File

System Files

KMZ file extension

Google Earth Placemark File

GIS Files

MOBI file extension

Mobipocket eBook

eBook Files

NES file extension

Nintendo (NES) ROM File

Game Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TMP file extension

Temporary File

Backup Files

3G2 file extension

3GPP2 Multimedia File

Video Files