credit In one of my projects, I’m getting issues while connecting to AWS load balancers - I have written this post to secure my studies in this regard. We have an front end hosted on , with an behind which we have multiple each running a service behind an proxy. Angular 4 AWS S3 bucket AWS elastic load balancer EC2 servers pm2 nginx The REST requests from the front end reaches the server without issues: CORS without the elastic load balancer and directly to the server AWS EC2 The REST requests breaks with the CORS errors from the front end and not reaches the server: with the AWS elastic load balancer and not directly to the EC2 server Although we’re not yet successful but which we have tried so far: these are the stuff (as per @agentspacecake) Allowed CORS in the , example — done S3 bucket config Allowed CORS in the back end using — done CORS node module Allowed CORS in the — done nginx proxy using the CORS headers Allow CORS on the load balancer’s front — not done Based on my studies so far: Per @Max@AWS, we need to whitelist the “Origin” header Per @Brian@AWS, we’d want to whitelist the “Origin” and any other headers you’d like to forward This was a especially for chrome bug in the past As per @Arun@AWS, the requests needs to contain the headers which are expected to return Not sure if the browser caching could surface the CORS issue Per @hescar, we can also try adding a ‘Origin’ header Looks like, we shall not use * wildcard The AWS staff says that ELB doesn’t support CORS yet The to ELB CORS support still looks open feature request The says that the JSON is not allowed in simple/actual requests docs Content-Type Requests only use the GET or POST HTTP methods. If the POST method is used, then Content-Type can only be one of the following: application/x-www-form-urlencoded, multipart/form-data, or text/plain. Hope this helps to some extent.