UPDATE: 18 March 2021 – Back in 2014 when I wrote this post, it outlined an excellent new tool Comcast had released to compare the speed of your connection over IPv4 versus over IPv6. At the time they were rolling out IPv6 into their networks and were also active with a range of companies promoting IPv6 deployment.
In the seven years since, Comcast has completed their IPv6 deployment and also changed their speedtest tool to be more consumer-friendly – and it no longer compares IPv4 vs IPv6. If you would like to do that speed comparison, I recommend either of these sites:
- https://ipv6-test.com/speedtest/ (allows a choice of different test sites)
- http://www.speedtest6.com/
If you would like to see the original 2014 text, you can read the archived article.