Cross origin resource sharing means that when we try to access a from one origin from a different origin. To get more understanding we need to know what origin is or what exactly is considered while cors calls. The origin is determined based on the URL.If we have URL A (http://localhost:45376) and URL B (http://localhost:45376) and if URL A wants to access a api method on URL B than it wont be allowed under CORS restriction. now be advised that if you are running it on chrome you may get an Origin exception indicating that you are not allowed but if you are running on IE than the port is not considered so it will be allowed and you will be able to access the API method without CORS restriction.