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

EXE file extension

Windows Executable File

Executable Files

GED file extension

GEDCOM Genealogy Data File

Data Files

HTML file extension

Hypertext Markup Language File

Web Files

JS file extension

JavaScript File

Web Files

KML file extension

Keyhole Markup Language File

GIS Files

LOG file extension

Log File

Text Files

M4A file extension

MPEG-4 Audio File

Audio Files

MSG file extension

Outlook Mail Message

Text Files

PAGES file extension

Pages Document

Text Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

TEX file extension

LaTeX Source Document

Text Files

TXT file extension

Plain Text File

Text Files

WSF file extension

Windows Script File

Executable Files

ZIPX file extension

Extended Zip File

Compressed Files