title: Choosing between www.example.com and example.com
body: <p>I'm building a website from scratch.</p>
  
  <p>It seems desirable to me to have the "canonical" url be "<a href="http://example.com" rel="nofollow">http://example.com</a>" rather than the older-style "<a href="http://www.example.com" rel="nofollow">http://www.example.com</a>". My rationale is that shorter is easier to type, especially on mobile.</p>
  
  <p>However, I see some large sites that do not do this. For instance, if you navigate to "<a href="http://zillow.com" rel="nofollow">http://zillow.com</a>", you will be redirected to "www.zillow.com".</p>
  
  <p>What is the reason for this?</p>
  
  <p>Does lopping off the www come back to bite you when you go to register an SSL cert? (wildcard vs. single subdomain?)</p>
  
  <p>Is it for compatibility with older browsers/devices/libraries/plugins?</p>
  
  <p>More importantly, is lopping off the www kosher with regards to web standards?</p>