But what about the opposite situation: an IPv6-only Web server? Can Cloudflare deliver its content to IPv4-only clients?
I'm not aware of any real business need for this at present, but as the world migrates to IPv6, this will be a common situation within a few years.
A student tested this several months ago, and it didn't work: his IPv6-only site was not available over IPv4, even when proxied through Cloudflare.
I am happy to say this has now been fixed, as demonstrated below.
If you click the link below to open the page, you will get a "server not found" error, unless you have IPv6 Internet service:
The server named "games6" uses the same AAAA address, but it is proxied through Cloudflare. As you can see, Cloudflare provides both A and AAAA proxy addresses:
If you click the link below to open the page, you will see the page. Notice the box in the upper right, indicating that Cloudflare's proxy server fetched this page via IPv6: