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

BIN file extension

Binary Disc Image

Disk Image Files

BMP file extension

Bitmap Image File

Raster Image Files

CER file extension

Internet Security Certificate

Web Files

CFG file extension

Configuration File

Settings Files

CSV file extension

Comma Separated Values File

Data Files

GIF file extension

Graphical Interchange Format File

Raster Image Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M4V file extension

iTunes Video File

Video Files

MPG file extension

MPEG Video File

Video Files

PIF file extension

Program Information File

Executable Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RAR file extension

WinRAR Compressed Archive

Compressed Files

SDF file extension

Standard Data File

Data Files

TAR file extension

Consolidated Unix File Archive

Data Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files