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

CER file extension

Internet Security Certificate

Web Files

CLASS file extension

Java Class File

Developer Files

DDS file extension

DirectDraw Surface

Raster Image Files

EXE file extension

Windows Executable File

Executable Files

KEY file extension

Keynote Presentation

Data Files

MDB file extension

Microsoft Access Database

Database Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

NES file extension

Nintendo (NES) ROM File

Game Files

ODT file extension

OpenDocument Text Document

Text Files

PDF file extension

Portable Document Format File

Layout Files

PL file extension

Perl Script

Developer Files

PRF file extension

Outlook Profile File

Settings Files

SVG file extension

Scalable Vector Graphics File

Vector Image Files

VB file extension

VBScript File

Executable Files

WMA file extension

Windows Media Audio File

Audio Files