In order to preserve cookies across primary domain and its sub domains with or without www and between http and https, you can check out a piece of asp.net written in C# code below:
1. Writing Cookie
Example below will write a cookie “your_cookie_name ” with value “your cookie value” and set the cookie’s domain property to yourdomain.com:
string cookie_str = "your cookie value"; Response.Cookies["your_cookie_name"].Value = cookie_str; Response.Cookies["your_cookie_name"].Domain = "yourdomain.com";
2. Reading Cookie
Response.Write("Your cookie has been written with value: " + HttpContext.Current.Request.Cookies["your_cookie_name"].Value.ToString());
The cookie will then be available to the primary domain (yourdomain.com) as well as to all its sub domains such as: subdomain1.yourdomain.com, subdomain2.yourdomain.com, etc.
It’s also available when you try to access through HTTP or HTTPS with or without www such as: https://yourdomain.com or https://www.yourdomain.com