That’s not really true, and here’s why.
Some browserslike Firefox 3handled IPv6 poorly in the past.
In those broken instances, disabling IPv6 was the best fix at the time.
Disabling IPv6 would bypass those speed bumps.
In fact, disabling IPv6 manually can actually create more problems.
For more informationand to see some benchmark tests that debunk the mythcheck the link below.
No, Disabling IPv6 Probably Won’t Speed Up Your Internet Connection| The How-To Geek