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

AIF file extension

Audio Interchange File Format

Audio Files

ASP file extension

Active Server Page

Web Files

DOCX file extension

Microsoft Word Open XML Document

Text Files

JPG file extension

JPEG Image

Raster Image Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

KMZ file extension

Google Earth Placemark File

GIS Files

PPT file extension

PowerPoint Presentation

Data Files

PRF file extension

Outlook Profile File

Settings Files

ROM file extension

N64 Game ROM File

Game Files

SWF file extension

Shockwave Flash Movie

Video Files

SYS file extension

Windows System File

System Files

THM file extension

Thumbnail Image File

Raster Image Files

WAV file extension

WAVE Audio File

Audio Files

XCODEPROJ file extension

Xcode Project

Developer Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files