Sure, messy, but would generally work. I guess they could also move this checking to the user agent (because they control Chrome) to have the check performed b

Sure, messy, but would generally work. I guess they could also move this checking to the user agent (because they control Chrome) to have the check performed before the user is actually waiting for results and milliseconds matter. Introduce some ugly but pragmatic HTTP header, like "Accept-IP: v6". :) So, this way they could serve v6-only results reliably to clients that can access either both v4 and v6. (People who can only access v6.. that must be a very special kind of people.)