I was testing something in Chrome on a Mac and I wanted to be sure IPv6 was not cause of the issue. In Firefox you have the option to disable IPv6 by browsing to about:config and toggle the preference name network.dns.disableIPv6 to the value true.
Within Chrome I was not able to find such an option. The alternative is to start Chrome with the --disable-ipv6 option. for Mac the complete line to start Chrome via the terminal is:
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --disable-ipv6
You can check for example on www.whatismyipv6.com to test this.