Web and XML Glossary

In the context of the WWW, an HTTP Proxy is an intermediary program which acts as both an HTTP Server and an HTTP Client, receiving a request from a Client (in most cases a Browser) and then acting as an HTTP Client and making requests on behalf of other HTTP Clients. However, requests to an HTTP Proxy can also be serviced internally, for example if the HTTP Proxy uses its Cache instead of sending a request to the origin HTTP Server. In order to use an HTTP Proxy, the HTTP Client's request has to be explicitly addressed to the HTTP Proxy, which then sends a request to the origin HTTP Server. An HTTP Proxy may also perform a protocol conversion, for example a Browser may send an HTTP request to the HTTP Proxy referencing an FTP resource, and the HTTP Proxy then acts as FTP Client to retrieve the resource from the FTP Server using FTP, and eventually the resource is sent back from the HTTP Proxy to the Browser using HTTP.