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

CAB file extension

Windows Cabinet File

System Files

CRDOWNLOAD file extension

Chrome Partially Downloaded File

Misc Files

CSS file extension

Cascading Style Sheet

Web Files

HTML file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

ICS file extension

iCalendar File

Misc Files

KMZ file extension

Google Earth Placemark File

GIS Files

MAX file extension

3ds Max Scene File

3D Image Files

PAGES file extension

Pages Document

Text Files

PPS file extension

PowerPoint Slide Show

Data Files

PRF file extension

Outlook Profile File

Settings Files

TGA file extension

Targa Graphic

Raster Image Files

TXT file extension

Plain Text File

Text Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files