What should a proxy pass in the Host header?

Question

Today I found out that $host and $http_host differ. At least $host doesn't contain the port number. Although there's more to it. My understanding is that people usually do proxy_set_header Host $host, which is... wrong? Is there some sort of general guideline?

Answer 1

nginx-proxy has proxy_set_header Host $http_host in its config. Sounds like an authoritative source to me.