A plug-in is a library that extends or changes the behavior of Illustrator. On Windows, a plug-in is built as a DLL (dynamic-link library). On Macintosh, a plug-in is built as a bundle that contains a shared library. The plug-in architecture in Illustrator is very powerful. Plug-ins have access to Illustrator’s elegant vector, text, and raster engines, as well as Illustrator’s user interface. The API is a fundamental part of the application; in fact, most of Illustrator itself is implemented as plug-ins. You can create plug-ins that add new tools to the drawing, shading, and raster tools already in Illustrator. Plug-ins can turn Illustrator into a powerful CAD, cartographic, or other custom design application. Users can add or remove plug-ins to quickly and easily customize Illustrator to their needs.

The Illustrator API offers several benefits to plug-in developers. Because Illustrator handles large application tasks like printing and saving files, you can concentrate on the implementation of your plug-in’s unique features. Plug-ins do not need to support undo or window updating; these are handled by the API and are invisible to the plug-in. This translates into shorter development cycles.

Your plug-in also can take advantage of Adobe Dialog Manager (ADM), a cross-platform, user-interface API. Plug-ins that use ADM floating panels are completely integrated with Illustrator; the panels can be docked, undocked, and controlled as if they were built into Illustrator.

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