What does this test check?
Your browser opens a few small test addresses, the way it opens any site:
IPv4-only and IPv6-only sites: can you reach each internet, and from which address.
A dual-stack site (it has both): which one your browser picks, and whether it waits for IPv6 before giving up.
Large packets over IPv6: a request big enough to need full-size packets, on a new connection. Where the path MTU is broken, small requests work and large ones vanish, which shows up as pages that hang.
Addresses with no name, one IPv6 and one IPv4: whether IPv6 works without DNS, and whether you are on an IPv6-only network with NAT64.
Each test asks two or three providers at once (DNSPod, icanhazip, Cloudflare, ipify) and takes the first answer, so one provider being blocked or slow doesn't fail it.
How is the score counted?
Out of 10, after test-ipv6.com's idea of how ready a network is for IPv6: 4 points when IPv6-only sites work, 2 when large packets get through over IPv6, 2 when dual-stack sites open without waiting, 1 when IPv6 works without DNS, 1 when your browser picks IPv6. One point off when IPv6 takes more than 3 seconds to answer. With no IPv6 at all, the score is 0, even though every site still works over IPv4.
10 means IPv6 works everywhere and slows nothing down.
I have no IPv6. How do I get it?
Most providers offer IPv6 now; it is often just turned off. In your router's admin page, look for IPv6 (or WAN → IPv6) and set it to the mode your provider uses, usually DHCPv6 or "native", with prefix delegation on. Then make sure the LAN side hands out IPv6 addresses (SLAAC or DHCPv6).
If the router has no IPv6 setting, or the provider doesn't offer it, ask them. On a phone, mobile data usually has IPv6 even when Wi-Fi doesn't.
Without IPv6, every site still works over IPv4: nothing is broken, you just miss the sites and apps that are IPv6 only.
IPv6 works but IPv6-only sites fail. Why?
Then the IPv6 connection is fine but your DNS doesn't return IPv6 addresses (AAAA records), so your browser never learns that the site has one. Common causes: a router setting that filters AAAA records (some routers in China have it, often on by default), a DNS server that drops them, or a proxy that answers DNS itself.
Turn off AAAA filtering in the router, or set a public DNS such as 1.1.1.1, 8.8.8.8 or, in mainland China, 223.5.5.5.
What is the large packet test (MTU)?
Data travels in packets of up to about 1,500 bytes. On some IPv6 paths (tunnels, PPPoE, misconfigured routers) full-size packets are too big for one link, and the message that says "send smaller ones" is blocked. Small requests work, so the connection looks fine, but large pages, images or downloads hang forever.
The test sends a 3.5 KB request to an IPv6-only host on a new connection, which needs full-size packets both ways. If it fails while the small IPv6 test passes, lower the MTU on your router's IPv6 or WAN settings (try 1,480 or 1,452 for PPPoE), or ask your provider.
Why does my browser pick IPv4 when IPv6 works?
Browsers try both and take whichever connects first (Happy Eyeballs). If IPv4 wins, IPv6 is slower to connect on your network, or your system prefers IPv4: Windows does that for tunnelled IPv6 (6to4, Teredo), and many proxies and VPN apps carry only IPv4. Nothing is broken; IPv6-only sites still open.
I use a proxy or VPN. Whose result is this?
Mostly the proxy's. With a proxy on, the test sites are reached through it, so the addresses and the IPv6 support shown are those of the proxy server, and a proxy that carries only IPv4 makes IPv6 look missing. To test your own network, turn the proxy off (or send these hosts direct) and test again.
What is an IPv6-only network with NAT64?
Some mobile networks give phones IPv6 only. To still reach IPv4-only sites, their DNS makes up an IPv6 address for those sites (DNS64), and a gateway translates (NAT64). Sites open by name, but an IPv4 address typed directly can't be reached, which is what the test spots. It is a normal setup and works for almost everything.
Is my data collected?
No. The tests go straight from your browser to the test hosts, which see your address as with any site. This site receives no results; a shared link carries only the score and the test times, never your addresses. The code is open source on GitHub.
