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

ASP file extension

Active Server Page

Web Files

ASPX file extension

Active Server Page Extended File

Web Files

CBR file extension

Comic Book RAR Archive

Compressed Files

CSS file extension

Cascading Style Sheet

Web Files

DAT file extension

Data File

Data Files

DDS file extension

DirectDraw Surface

Raster Image Files

DMP file extension

Windows Memory Dump

System Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JSP file extension

Java Server Page

Web Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

MOV file extension

Apple QuickTime Movie

Video Files

PL file extension

Perl Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

RTF file extension

Rich Text Format File

Text Files

WSF file extension

Windows Script File

Executable Files