Well, as mentioned in many websites we really can't read http headers at the client side (using javascript) if the call is not initiated by itself. If client side application initiates a http request then it is possible to set headers in the request and read headers from the response. So that answers it all, although there are few workarounds (that I read as part of this investigation) such as using workerservice etc. I have come to the conclusion to change our design. (i.e. calling identity management system to request for specific detail instead of trying to read from http headers.)