Guides/IPv4 vs IPv6
IPv4 vs IPv6
IPv4 and IPv6 are two versions of the Internet Protocol—the numbering system that lets devices find each other online. Your connection may use one, the other, or both at the same time (dual-stack). Understanding the difference helps you interpret IP checker results and decide whether “Unavailable” on one family is a real problem.
IPv4 in plain language
IPv4 addresses look like 203.0.113.10. They have been the internet’s default for decades. Because the pool of IPv4 addresses is limited, ISPs often share them among customers with carrier-grade NAT, and many networks still prefer IPv4 for everyday browsing.
Most tutorials, firewall UIs, and game server setups still assume IPv4. That is why a dedicated IPv4 check remains useful even as IPv6 grows.
IPv6 in plain language
IPv6 addresses are longer and use hexadecimal groups separated by colons. They were designed to solve address exhaustion and to simplify some network features. Many mobile and fiber providers already give you a working IPv6 path even if you rarely notice it.
Privacy extensions can rotate the interface identifier so your full IPv6 address changes over time while staying in the same prefix. Reloading an IPv6 checker twice may show two different addresses that still belong to you.
Dual-stack: both at once
Dual-stack means your device and ISP can speak both protocols. Operating systems pick a preference order (often Happy Eyeballs) so pages load on whichever path works first. That is why a single page request might arrive over IPv6 even though you also have a working IPv4 address.
getwhatismy.com therefore probes IPv4-only and IPv6-only hostnames in addition to the main page load. Seeing both results is the reliable way to know what your ISP actually provides.
When one family shows Unavailable
Unavailable on IPv6 usually means no working route to our IPv6-only host right now—not that the whole internet is broken for you. Many networks are still IPv4-only. Unavailable on IPv4 can mean an IPv6-only path, a DNS issue for the IPv4 probe host, or a firewall blocking that check.
Everyday browsing rarely requires you to “fix” a missing family unless a specific service demands it. Use the dual-stack home check when you are validating a new router, VPN, or ISP install.
What to do next
Compare the [home IP check](/), the dedicated IP address page, and the family-specific tools. If you use a VPN, test with it on and off—some exits are IPv6-only or IPv4-only. Router firmware updates and ISP “IPv6” toggles are the usual place to enable a missing family at home.