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

JSP file extension

Java Server Page

Web Files

LNK file extension

Windows File Shortcut

System Files

XLS file extension

Excel Spreadsheet

Spreadsheet Files

7Z file extension

7-Zip Compressed File

Compressed Files

MPG file extension

MPEG Video File

Video Files

ICO file extension

Icon File

System Files

IFF file extension

Interchange File Format

Audio Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

IBOOKS file extension

Multi-Touch iBook

Data Files

DXF file extension

Drawing Exchange Format File

CAD Files

TIF file extension

Tagged Image File

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

BAK file extension

Backup File

Backup Files

DESKTHEMEPACK file extension

Windows 8 Desktop Theme Pack File

System Files