A file containing data used to alter, enhance, or extend the operation of a parent application program. One of the first uses of this term was in silicon beach's superpaint application (late 1980s?) for the macintosh. It had a Plug-ins folder containing different tools and effects.

The netscape navigator world-wide web browser supports plug-ins which display or interpret a particular file format or protocol such as shockwave, realaudio, adobe systems, inc. pdf, corel cmx (vector graphics). The file to be displayed is included in a web page using an EMBED html tag.

Plug-ins, both commercially and indepently authored, can usually be downloaded for free and are stored locally. Plug-ins come in different versions specific to particular operating systems (microsoft windows 3.1, 3.2, and macintosh are available).

Compare applet.

plug-in plaza.

pc mag plug-ins.