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

ACCDB file extension

Access 2007 Database File

Database Files

BAK file extension

Backup File

Backup Files

CGI file extension

Common Gateway Interface Script

Executable Files

COM file extension

DOS Command File

Executable Files

DTD file extension

Document Type Definition File

Developer Files

EPS file extension

Encapsulated PostScript File

Vector Image Files

HTML file extension

Hypertext Markup Language File

Web Files

IBOOKS file extension

Multi-Touch iBook

Data Files

JAVA file extension

Java Source Code File

Developer Files

LNK file extension

Windows File Shortcut

System Files

PIF file extension

Program Information File

Executable Files

RSS file extension

Rich Site Summary

Web Files

SYS file extension

Windows System File

System Files

XCODEPROJ file extension

Xcode Project

Developer Files

XML file extension

XML File

Data Files