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

CFM file extension

ColdFusion Markup File

Web Files

DAT file extension

Data File

Data Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GED file extension

GEDCOM Genealogy Data File

Data Files

GZ file extension

Gnu Zipped Archive

Compressed Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JPG file extension

JPEG Image

Raster Image Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MAX file extension

3ds Max Scene File

3D Image Files

MDB file extension

Microsoft Access Database

Database Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

SYS file extension

Windows System File

System Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

WAV file extension

WAVE Audio File

Audio Files

WMA file extension

Windows Media Audio File

Audio Files