IPv6 Test

IPv6 adoption varies from country to country and provider to provider, and a connection that looks fine for ordinary browsing may still have no working IPv6. The page tests it from where it matters, your browser, by asking whether a server that can be reached only over IPv6 answers, and shows the public address each protocol reveals.

What happens when you press the button

The page makes two requests. One goes to api4.ipify.org, a name that has only an IPv4 address, so the request must travel over IPv4. The other goes to api6.ipify.org, which has only an IPv6 address, so it can succeed only if your connection has working IPv6 all the way. Both services reply with the address they see, the way every website does. The page shows each reply with the time it took. If both succeed, you have dual stack. If only the first, you have IPv4 only; if only the second, which is rare, IPv6 only, perhaps with a translation service.

Reading the verdict

A dual-stack result means your browser can use either protocol. Browsers try IPv6 first when a site offers it, falling back quickly to IPv4 if IPv6 is slow; this behaviour is called Happy Eyeballs and is specified in RFC 8305. “IPv4 only” means the IPv6 request failed or timed out, which points at a missing global address, a router that does not advertise a route, a provider that does not offer IPv6, or a filter. The times let you compare the paths: IPv6 is not always faster, and a large gap can reveal a tunnel.

Addresses that move

An IPv6 address from this test is usually unique to your device. Because operating systems prefer temporary addresses for outgoing connections (RFC 8981), it changes from time to time, and a different network gives a different prefix. A static address for a server uses a different mechanism. Your IPv4 address, by contrast, is usually shared by everything behind your router through NAT, so the two protocols show different things: the IPv4 line identifies the household, the IPv6 line a device.

What a pass does not show

The result describes this browser at this moment. Another device may behave differently if its stack, firewall or VPN differs. A pass only shows you can reach one particular server over IPv6; it cannot guarantee that every site works, because routes and peering differ. DNS also plays a part, since a site is reached over IPv6 only if it publishes an AAAA record, which you can check with the AAAA Record Lookup.

A worked example

On a dual-stack home connection the page lists two rows. “IPv4-only endpoint” shows a dotted address and a time of a few hundred milliseconds; “IPv6-only endpoint” shows a colon-separated address with its own time. The verdict reads “Dual stack: your connection works over both IPv4 and IPv6”. On an IPv4-only network the second row shows a failure, and the verdict says IPv6 is not reachable.

Limits

The test relies on a third-party service being reachable, so a failure of that service looks like a failure of your IPv6. Network filters, VPNs and proxies affect the result and the addresses shown. It does not test throughput, MTU problems on IPv6 paths or DNS64 and NAT64 arrangements. For ready-made address conversions between the two protocols use the IPv4 to IPv6 Converter.

Related tools

• AAAA Record Lookup checks whether a domain publishes IPv6 addresses.
• IPv4 to IPv6 Converter shows mapped and NAT64 forms.
• IPv6 Compressor shortens the address you obtained.
• WebRTC Leak Test shows which of your addresses a web page can learn.