I would like to add a custom header to the responses generated by an Elastic Load Balancer. This custom header should contain the EC2 instance ID (something like X-EC2-Instance-ID=123456) corresponding to the backend who has handled the request.

Is it possible to do this from the ELB itself, without configuring this header on each backend server?

thanks!

It isn’t possible to accomplish this at the ELB. You would have to add this at the EC2 level.