From what I understand you have to add these in to the index.php or the .htaccess file which is generated by UE4.
I’ve tried various ways adding it to .htaccess with no luck. With quotes, without quotes, ect.
Header always set Access-Control-Allow-Origin: "*"
Header always set Access-Control-Allow-Methods: "GET, HEAD, POST, CONNECT, PUT, OPTIONS"
Header always set Access-Control-Allow-Headers: "content-type, pragma, x-unrealengine-agent"
However, what the kicker seems to be is that it is a “preflight” request requiring some php code I haven’t gotten to work just yet. I’ve seen some places where they say only the .htaccess file is required but it has yet to work for me.
edit: Also note I am testing with my game uploaded to an FTP (not the HTML5LaunchHelper.exe)