I've created a webserver that handles http from a game I have in Itch.io.
I was trying to enable CORS to only allow requests from my subdomain, like arknostik.itch.io
Viewing post in Can I set CORS to my Itch.io subdomain?
I think you have it backwards, it doesn't make sense to add CORS to itch.io since you wouldn't be making requests there. We don't have a server running on our domain that would know how to respond to your request. If you want to have your game communicate with your own domain you would want to add CORS to your domain