IPv6 adoption keeps climbing, but most people still have no idea whether their own connection actually uses it. Your ISP may advertise "IPv6 ready" while your router silently falls back to IPv4 for everything. The only way to know is to test.
I rounded up the best free online tools for checking IPv6 connectivity, plus a few bonus network diagnostics worth bookmarking. All of them run in the browser — no installs, no sign-ups.
1. 17NAS IPv6 Test — Best Overall
Link: https://17nas.com/ipv6-test.php
The most complete free option I found. It checks your IPv4 and IPv6 addresses side by side, measures latency on both protocols so you can see which is actually faster on your connection, identifies your ISP and ASN, and tells you whether you're on dual-stack, IPv4-only, or IPv6-only. The connection quality score is a nice touch — one number summarizing how healthy your IPv6 path is.
What sets it apart: there's also a free no-auth API (ip.17nas.com) returning JSON, which is handy for scripts and server monitoring. No registration required for anything.
2. Test-IPv6.com — The Classic
Link: https://test-ipv6.com
The long-standing reference test, run by Jason Fesler. It gives you a 0–10 score for IPv6 readiness and detects common transition mechanisms (Teredo, 6to4). The interface is dated but the test itself is solid and widely trusted. Good second opinion after any other test.
3. IPv6-test.com — Best for Detail Lovers
Link: https://ipv6-test.com
Validates your IPv6 address, checks for common misconfigurations, and shows detailed protocol information. If you want to dig into the technical details of your connection rather than just getting a pass/fail, this is the one.
4. Cloudflare's IPv6 Test — Quickest Check
Link: https://www.cloudflare.com/ssl/encrypted-sni/ (see also their connectivity diagnostics)
Cloudflare runs several quick connectivity checks. Fast, no frills, and you can trust the infrastructure behind it. Best when you just want a yes/no answer in five seconds.
5. 17NAS NAT Test — Best Companion Test
Link: https://17nas.com/nat-test.php
IPv6 is only half the story for gamers and VoIP users — NAT type matters just as much. This free test detects your NAT type and shows your public IP, which determines whether peer-to-peer connections (gaming, video calls, file sharing) will work smoothly or need relaying. Pairs naturally with the IPv6 test above.
6. 17NAS Port Check — For the Self-Hosters
Link: https://17nas.com/port-check.php
Running a home server or NAS? This checks whether a TCP port is actually reachable from the internet — the fastest way to confirm your port forwarding works. Free, no signup.
7. MXToolbox — Best All-Rounder for DNS/Network Pros
Link: https://mxtoolbox.com
Not strictly an IPv6 tester, but the Swiss Army knife of network diagnostics: DNS lookups, MX records, blacklist checks, and more. If you do any server administration, you already know it.
How to Read Your Results
- Dual-stack with IPv6 preferred: ideal. You're getting the full modern internet.
- IPv4-only: common, especially on older routers or ISPs that haven't enabled IPv6 on your line. Check your router settings — many support IPv6 but ship with it off.
- IPv6-only: rare for residential connections; more common in mobile networks and some enterprises.
- Teredo/6to4 detected: transition tunnels. They work, but native IPv6 is better — consider it a hint to configure things properly.
Bottom Line
Start with the 17NAS IPv6 Test for the full picture, cross-check with Test-IPv6.com, and keep the NAT and port tools bookmarked if you game or self-host. All free, all in the browser, no accounts needed.
Found this useful? The author builds free network tools at 17NAS.
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