Is it up to me having www in my web domain?

Question

every page domain begin with http:// or https:// no matter what. but in some web page there is no www after that, while others have it. Is it up to me having it or not. when can i decide that?

amazon have it http://www.amazon.com/ while no tumblr page haven't one http://f-l-e-u-r-d-e-l-y-s.tumblr.com/

note: tumblr hasn't www because it has subdomains?

Answer 1

It's up to you indeed. In http://www.amazon.com/, amazon.com is the domain name. http:// or https:// define the protocol (https = secured http). It's not part of the domain name. www is a subdomain. you may have multiple subdomains for a given domain - or no subdomain.