A third-party software product, such as a search toolbar, that is integrated into a Web browser to extend its capabilities. A "helper application" provides similar capabilities to a browser plug-in, but runs as an external application and typically launches another window for viewing. The terms browser plug-in and helper application are often used synonymously, but the browser may give them a different priority. For example, in order to handle an unknown file type, it may check its plug-in list before looking for a helper application.