In
computing, a
plug-in (or
plugin,
add-in,
addin,
add-on,
addon, or
extension) is a
software component that adds a specific feature to an existing
computer program. When a program supports plug-ins, it enables customization. The common examples are the plug-ins used in
web browsers to add new features such as search-engines, virus scanners, or the ability to use a new
file type such as a new video format. Well-known browser plug-ins include the
Adobe Flash Player, the
QuickTime Player, and the Java plug-in, which can launch a user-activated
Java applet on a web page to its execution on a local
Java virtual machine.