(Netscape Plug-in API) A programming interface for browser plug-ins originally developed by Netscape. The plug-in identifies the content it supports, and when that data must be rendered, the browser launches the appropriate plug-in. For example, clicking a PDF file in the browser launches the Adobe Acrobat Reader plug-in. Superseded by the Pepper Plug-in API (PPAPI), newer Web browsers no longer support NPAPI. See NSAPI, PPAPI and Netscape.