How to set cookies in Magento for WWW domain

Question

I'm trying to make sure I have set the Cookie Domain correctly. I have my website set up for https://www.example.com. I have the Cookie Domain right now set like this: .example.com When I look at the cookies in Chrome I see cookies like .www.example.com (from _ga I think that is Google Analytics), and some like this, www.example.com (from cookies_lhc.js, that is from my Live Help Chat), and some like this: .example.com from "frontend". The way I understand it, is that the "dot" stands for subdomains and www is considered a subdomain. I read elsewhere that I need to set the cookies like this: .www.example.com but that seems strange as any subdomains would be sub.www.example.com, but subdomains would really be like www.sub.example.com ...correct?

When I set the cookies like wwww.example.com without the dot I can't log in Magento admin. But I don't understand why Google adds cookies .wwww.example.com It looks like all these cookies need to be the same. I seems to work the way I have it but I don't have any subdomains set up yet (I have to upgrade my hosting for that, but soon). I don't know if there are long term ramifications to getting this wrong, there isn't really much information I can find on it. So should it be

www.example.com, .example.com, or .www.example.com

Do all the cookies need to match?

Answer 1

No, they don't need to match.

The cookie domain defined, where the browser sends the cookies to:

• www.domain.com means the cookie is only sent to www.domain.com
• .domain.com sends the cookie to domain.com (I think) and every suddomain, so you can exchange informations between different subdomains/servers

Answer 2

To provide a little update
According to MDN:

Contrary to earlier specifications, leading dots in domain names are ignored, but browsers may decline to set the cookie containing such dots. If a domain is specified, subdomains are always included.

https://developer.mozilla.org/en-US/docs/Web/API/Document/cookie#new-cookie_domain

So in conclusion, leading dot should be omitted, and subdomains will always be included.
e.g. example.com