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

ACCDB file extension

Access 2007 Database File

Database Files

ASP file extension

Active Server Page

Web Files

BMP file extension

Bitmap Image File

Raster Image Files

DMP file extension

Windows Memory Dump

System Files

FON file extension

Generic Font File

Font Files

JS file extension

JavaScript File

Web Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KML file extension

Keyhole Markup Language File

GIS Files

M4V file extension

iTunes Video File

Video Files

MSG file extension

Outlook Mail Message

Text Files

TARGZ file extension

Compressed Tarball File

Compressed Files

TIFF file extension

Tagged Image File Format

Raster Image Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

3GP file extension

3GPP Multimedia File

Video Files