Software plug-ins are miniature programs that “plug into” a host program for additional functionality. Plug-ins allow a third-party application to be used within the host program, acting as a kind of liaison or bridge. There are many kinds of plug-ins, but one that many Web surfers will be familiar with is the Acrobat Reader&trade plug-in for Web browsers. This allows .pdf files to be read within the browser window. Other popular browser plug-ins include QuickTime™ to view movies, and the Flash™ plug-in to view Flash scripts.

Email programs can utilize various plug-ins to provide secure levels of encryption. These plug-ins work in conjunction with Pretty Good Privacy (PGP), the premiere encryption software on the Internet. Installing a PGP plug-in to an email application adds encryption-related icons to the toolbar menu. These additional icons allow easy access to instant encrypting and decrypting of emails, though an email client can also be configured to perform these functions automatically. PGP must be installed prior to installing a PGP plug-in.

In many cases graphics programs require plug-ins to support proprietary file formats. For example, Adobe™ Photoshop™ uses a unique format. To view a saved file from Photoshop in another graphics program, the program will likely require a plug-in that adds this capability. There are also plug-ins that can be used in Photoshop, Paint Shop Pro™ and other paint programs to extend the effects menus for creating unique and professional results.

Media players use plug-ins to support various audio file formats and to extend functionality. In this category, some plug-ins decode media data, some provide additional visualization capability, and other plug-ins add effects filters like reverb and equalization to the media player.

Secondary plug-ins can help primary plug-ins work better or faster. If you’ve ever been frustrated with how long it takes an Adobe .pdf file to open inside your browser, there are plug-ins available to speed up the process. Other plug-ins provide shortcuts to deeply buried menu items, such as the ability to clean your browser cache with the click of a conveniently placed button.

To find plug-ins use the search box of your favorite download site. You can find plug-ins for a specific program by entering the name of the program, a plus sign and the word “plug-ins,” such as Explorer +plug-ins in any search engine. Plug-ins might also be referred to as “add-ons,” an umbrella term used by Mozilla Firefox to include plug-ins, themes and add-ons for that browser.