If you see a happy smiley covering an unhappy smiley, then you have IPv6. If you only see an unhappy smiley, then you have only IPv4.

It may also happen that you see two sad smileys, in that case you probably also don't have IPv6 connectivity but you also use a Firefox browser that has a serious HTTP/2 connection reuse bug. In that case we highly recommend to stop using Firefox until they fixed that bug. UPDATE: It seems like the Firefox developers in charge think that it is not a problem if network traffic is sent to an IP address that doesn't match the hostname, see Bug 1763632. And see also Bug 1420777.

Let's also see if your current DNS server supports connecting to IPv6-only DNS servers:

If you don't have IPv6, ask your internet provider to enable it. Also point out RFC6540. You might also consider to switch over to a different provider who offers IPv6.

You might also check this site for a similar test.

Feel free to mark this page as your browser startup site, so that the smileys always indicate if you can be happy with your current internet connection.