If you Google for "what is my ip?" then Google will tell you. If it looks like "12.34.56.78" (known as "dotted quad") then your computer is using IPv4. If it looks like "FE80:0000:0000:0000:0202:B3FF:FE1E:8329" or "FE80::0202:B3FF:FE1E:8329" then you are using IPv6.

Try http://en.internet.nl/ as a way to find whether your sites or ISPs use IPv6

I use a Chrome plugin called IPvFoo. https://chrome.google.com/webstore/detail/ipvfoo/ecanpcehffn...

This is the one I use:

http://ipv6-test.com/validate.php