Among other things, this document describes systems, methods and devices for providing a cloud proxy auto-config (PAC) function for clients connected to a private network, such as an enterprise network. The teachings hereof are of particular use with cloud hosted proxy services provided by server deployments outside of the private network (e.g., external to the enterprise or other organizational network). This document also describes systems, methods and devices for providing a proxy auto-config (PAC) function for clients connected to a third party network, such as when the client moves outside of the enterprise network.