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

CBR file extension

Comic Book RAR Archive

Compressed Files

CS file extension

Visual C# Source Code File

Developer Files

DLL file extension

Dynamic Link Library

System Files

FLV file extension

Flash Video File

Video Files

FNT file extension

Windows Font File

Font Files

JAVA file extension

Java Source Code File

Developer Files

JSP file extension

Java Server Page

Web Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

NES file extension

Nintendo (NES) ROM File

Game Files

RTF file extension

Rich Text Format File

Text Files

TAX2012 file extension

TurboTax 2012 Tax Return

Data Files

TORRENT file extension

BitTorrent File

Misc Files

XLR file extension

Works Spreadsheet

Spreadsheet Files