Cookie - Scope

About

The scope of a cookie name is a calculated property defined by the concatenation of

If the request URL matches the scope (ie domain and path expression), the user agent (browser) will add the cookies in the Cookies header to the request returning it to the server (if the other cookie property (such as expiration date, http only,..) are also valid)

You can have the same name below differents scope.

Below you can see that their is 2 cookie named visits below two differents scopes.

For instance:

A cookie that should be returned to every path and every subdomain of example.com would be set by the server with the following set-cookie response header

Set-Cookie: key=value; Path=/; Domain=example.com

then when the user-agent (browser) creates an HTTP request for the domain example.com, it will add in the request the following Cookies request headers

Cookies: key=value

The domain attribute determines the scope and determine which host (port excluded) are allowed to receive the cookie.

The scope rules are applied top down (ie applied to the domain and all subdomain)

if the value of the Domain attribute is:
- example.com
the user agent (browser) will include the cookie to request on the domain and all subdomain. ie
- example.com,
- www.example.com,
- and www.corp.example.com

If the domain property of the cookie is:

The path attribute is a scope attribute and is matched against the request URL path where:

The default value of the path is the parent of the last name:

If several cookies shares the same name with different path, a list of values is returned ordered by scope order. For instance, suppose that

Cookie: visits=2; visits=3

As seen in the Cookie value, there is no way to know the path of the values.