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

BAT file extension

DOS Batch File

Executable Files

C file extension

C/C++ Source Code File

Developer Files

CPL file extension

Windows Control Panel Item

System Files

HTML file extension

Hypertext Markup Language File

Web Files

INDD file extension

Adobe InDesign Document

Layout Files

KMZ file extension

Google Earth Placemark File

GIS Files

M4A file extension

MPEG-4 Audio File

Audio Files

PART file extension

Partially Downloaded File

Misc Files

PHP file extension

PHP Source Code File

Web Files

PLUGIN file extension

Mac OS X Plug-in

Plugin Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLR file extension

Works Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files