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

DOCX file extension

Microsoft Word Open XML Document

Text Files

CFG file extension

Configuration File

Settings Files

7Z file extension

7-Zip Compressed File

Compressed Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files

JAR file extension

Java Archive File

Executable Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

AIF file extension

Audio Interchange File Format

Audio Files

YUV file extension

YUV Encoded Image File

Raster Image Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

WSF file extension

Windows Script File

Executable Files

VCF file extension

vCard File

Data Files

DTD file extension

Document Type Definition File

Developer Files

PRF file extension

Outlook Profile File

Settings Files

INDD file extension

Adobe InDesign Document

Layout Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files