A returned resource may have one Access-Control-Allow-Origin header, with the following syntax: For requests that doesnt use credentials, literal value * can be specified, as a wildcard; this value tells browsers to allow requesting code from any origin to access the resource. +1 true, the OP specified Go lang, but I landed here and needed a solution for aspnet and this helped me, Actually, going to the Network tab will tell you nothing. To understand the reason, you should know two important facts: So if you allow application/x-www-form-urlencoded then hacker might place a