title: HTTP simultaneous connections per host limit... are per tab, browser instance or global?
body: <p>According to the HTTP Specification (w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.1.4), HTTP clients should limit their connections:</p>
  
  <blockquote>
    <p>Clients that use persistent connections SHOULD limit the number of simultaneous connections that they maintain to a given server. A single-user client SHOULD NOT maintain more than 2 connections with any server or proxy.</p>
  </blockquote>
  
  <p>Different vendors implement this limit differently: <a href="http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/" rel="noreferrer">http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/</a></p>
  
  <p>But. does this limitation applies per tab, per browser instance or globally for all the instances of the browser? Are pop-ups (dialogs) considered part of a tab or independent tabs?</p>
  
  <p>Same for websockets, does the limit on connections per origin applies per tab, browser instance or globally? </p>