[3] As of May 2011, IPv6 brokenness as measured by instrumenting a set of mainstream Norwegian websites was down to ~0.015%,[4] most of which was caused by older versions of Mac OS X which would often prefer non-working IPv6 connectivity when it was not justified.
[8] Google, a major provider of services on the Internet, experimented with using a type of DNS allowlisting on a per-ISP basis to prevent this[9][10] until the World IPv6 Launch.
[11] In 2010, several of the major web service providers met to discuss pooling their DNS allowlisting information in an attempt to avoid these scaling problems.
[12] It appears that no major content providers eventually ended up using the allowlisting approach, given that all that had previously declared an interest began serving AAAA records to generic DNS queries following World IPv6 Launch Day.
This is due to two factors: firstly, IPv6 transport is much improved, so that the underlying error rate is much reduced, and secondly, that common applications such as web browsers now use fast fallback methods such as the "Happy Eyeballs" algorithm to select whichever protocol works best.