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

CS file extension

Visual C# Source Code File

Developer Files

CSV file extension

Comma Separated Values File

Data Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

GZ file extension

Gnu Zipped Archive

Compressed Files

INDD file extension

Adobe InDesign Document

Layout Files

JAR file extension

Java Archive File

Executable Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MPG file extension

MPEG Video File

Video Files

MSG file extension

Outlook Mail Message

Text 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

TEX file extension

LaTeX Source Document

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files