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

HTM file extension

Hypertext Markup Language File

Web Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

GED file extension

GEDCOM Genealogy Data File

Data Files

CSR file extension

Certificate Signing Request File

Web Files

GAM file extension

Saved Game File

Game Files

DAT file extension

Data File

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

DBF file extension

Database File

Database Files

VCXPROJ file extension

Visual C++ Project

Developer Files

TORRENT file extension

BitTorrent File

Misc Files

TTF file extension

TrueType Font

Font Files

7Z file extension

7-Zip Compressed File

Compressed Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

3GP file extension

3GPP Multimedia File

Video Files