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

AVI file extension

Audio Video Interleave File

Video Files

COM file extension

DOS Command File

Executable Files

DBF file extension

Database File

Database Files

7Z file extension

7-Zip Compressed File

Compressed Files

KML file extension

Keyhole Markup Language File

GIS Files

H file extension

C/C++/Objective-C Header File

Developer Files

PL file extension

Perl Script

Developer Files

MPG file extension

MPEG Video File

Video Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

TIFF file extension

Tagged Image File Format

Raster Image Files

DLL file extension

Dynamic Link Library

System Files

DTD file extension

Document Type Definition File

Developer Files

M file extension

Objective-C Implementation File

Developer Files