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

ASF file extension

Advanced Systems Format File

Video Files

ASX file extension

Microsoft ASF Redirector File

Video Files

AVI file extension

Audio Video Interleave File

Video Files

CFG file extension

Configuration File

Settings Files

CUE file extension

Cue Sheet File

Disk Image Files

DMG file extension

Mac OS X Disk Image

Disk Image Files

DTD file extension

Document Type Definition File

Developer Files

ICS file extension

iCalendar File

Misc Files

IFF file extension

Interchange File Format

Audio Files

MOBI file extension

Mobipocket eBook

eBook Files

PKG file extension

Mac OS X Installer Package

Compressed Files

PRF file extension

Outlook Profile File

Settings Files

RTF file extension

Rich Text Format File

Text Files

VCF file extension

vCard File

Data Files

XLR file extension

Works Spreadsheet

Spreadsheet Files