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

BAK file extension

Backup File

Backup Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CLASS file extension

Java Class File

Developer Files

CPL file extension

Windows Control Panel Item

System Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

DEB file extension

Debian Software Package

Compressed Files

DEM file extension

Video Game Demo File

Game Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

GBR file extension

Gerber File

Data Files

INI file extension

Windows Initialization File

Settings Files

LOG file extension

Log File

Text Files

PDB file extension

Program Database

Database Files

RM file extension

Real Media File

Video Files

VCXPROJ file extension

Visual C++ Project

Developer Files

XLR file extension

Works Spreadsheet

Spreadsheet Files