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

CSS file extension

Cascading Style Sheet

Web Files

DNG file extension

Digital Negative Image File

Camera Raw Files

FNT file extension

Windows Font File

Font Files

GED file extension

GEDCOM Genealogy Data File

Data Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

M4A file extension

MPEG-4 Audio File

Audio Files

M4V file extension

iTunes Video File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

PDB file extension

Program Database

Database Files

PS file extension

PostScript File

Vector Image Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

YUV file extension

YUV Encoded Image File

Raster Image Files

3G2 file extension

3GPP2 Multimedia File

Video Files