What are technical/programming/non-SEO pros and cons of www or no-www, for domains as well as sub-domains? From Jeff Atwood's twitter at http://twitter.com/codinghorror/status/1637428313 : "sort of regretting the no-www choice because it causes full cookie submission to ALL subdomains. :(" What does this mean? Is there a blog post or article detailing this? What other specific issues and their reasons should be considered for www. vs no-www. Update: On searching for more info on this topic, I found following helpful ( in addition to Laurence Gonsalves answer ) : Dropping the WWW Prefix Impact on search results: Jivlain's and Isaac Lin's comments Use Cookie-free Domains for Components on StackOverflow : Should I default my website to www.foo or not? on StackOverflow : When should one use a ‘www’ subdomain?