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

ASF file extension

Advanced Systems Format File

Video Files

CER file extension

Internet Security Certificate

Web Files

DOC file extension

Microsoft Word Document

Text Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

EXE file extension

Windows Executable File

Executable Files

FLA file extension

Adobe Flash Animation

Developer Files

GZ file extension

Gnu Zipped Archive

Compressed Files

ICNS file extension

Mac OS X Icon Resource File

System Files

KEY file extension

Keynote Presentation

Data Files

KMZ file extension

Google Earth Placemark File

GIS Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PIF file extension

Program Information File

Executable Files

PKG file extension

Mac OS X Installer Package

Compressed Files

RTF file extension

Rich Text Format File

Text Files

TGA file extension

Targa Graphic

Raster Image Files