Client Addons that initiate a web search will use Internet Explorer rather than a user's preferred browser. This setting cannot be customized.
Client Addons are generally designed for workflow situations which involve item by item processing and are usually invoked on an item/request record form within the client. Common uses for custom Client Addons include search functionality of alternate resources (such as a catalog) in a web browser or through NCIP or Web API. These Addons are then often augmented to import information from the search results in the request/item form.
Addons allow you to add more functionality to the client. Addons are very flexible and allow you to designate your own tabs on a request form to perform actions, like a web search, based on information in the request. Once a result is found, you can update information in the client based on the results of your search.