A passive server-to-client data delivery system and method is provided. A web service request is received by a server from a client device requesting the performance of a web-based service. The identity of the client device is then ascertained and the server determines that new software is available for the requesting device. The server then performs the requested service and sets a flag indicating the availability of the new software. The response data, including the performed service, is supplemented with the flag data and returned to the client device. The client device, upon receipt of the supplemented response data then initiates a separate update request for the available software, which is then received by the client device and installed.