A server which acts as an intermediary between a set of browsers and the Web. When a Web page is requested by a browser it is first stored in the caching proxy server and then sent on to the browser that requested it. The server always ensures that popular pages requested by the browsers are stored locally in its file store. This means that access to these pages is very fast since there is no need for the pages to be brought across slow external communication lines. See also caching, proxy, and site caching. Caching proxy servers are also used for implementing firewalls.