How to make CORS-enabled HTTP requests in Angular 2?

In fact, it's not an Angular2 issue but a problem at the server side. The preflighted OPTIONS request needs to return an Access-Control-Allow-Origin header in its response.

Sending the Origin header in the original request will enable the CORS support on the server side. This header is automatically added by the browser when it detects that the domain of the request isn't the same as the caller's.

Be careful when implementing the preflight OPTIONS request on the server side since credentials aren't sent at this level. They are only sent within the target request. It seems to be the problem since you have 503 error. You're trying to check if the OPTIONS request is authenticated but it's not actually the case...

See this article for more details:

• http://restlet.com/blog/2015/12/15/understanding-and-using-cors/