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

ASPX file extension

Active Server Page Extended File

Web 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

JAVA file extension

Java Source Code File

Developer Files

KEY file extension

Keynote Presentation

Data Files

KEYCHAIN file extension

Mac OS X Keychain File

Data Files

MIM file extension

Multi-Purpose Internet Mail Message File

Encoded Files

PS file extension

PostScript File

Vector Image Files

PY file extension

Python Script

Developer Files

ROM file extension

N64 Game ROM File

Game Files

SLN file extension

Visual Studio Solution File

Developer Files

TGA file extension

Targa Graphic

Raster Image Files

WMA file extension

Windows Media Audio File

Audio Files

XHTML file extension

Extensible Hypertext Markup Language File

Web Files