A system is configured to authorize client access to an application programming interface (API) of a host device. A proxy is configured to handle network traffic between a host and a client. Clients engage the host through the proxy to access an API of the host. An authorized client-side application permitted use of the API includes an API request to the proxy. The proxy determines whether an internet protocol (IP) address of the client and the token match an existing IP-token pair. If no match exists, the proxy determines whether the token matches an existing token. The proxy authorizes the client access to the API when the IP and token match an existing pair or if the token does not match an existing token and the token is verified by the proxy.