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Glossary · VPN & tunneling

IPv6 leak

Also calledvpn ipv6 leak
Definition

An IPv6 leak is when a VPN protects your IPv4 traffic but your device still sends IPv6 traffic directly, exposing your real IPv6 address to websites.

Explanation

In depth

Most devices now have two addresses: an older IPv4 one and a newer IPv6 one. Many networks, and a large and growing share of Google's users, connect over IPv6 when it is available. A VPN that only routes IPv4 leaves IPv6 alone, so any site reachable over IPv6 is contacted directly and sees your real IPv6 address, which often identifies your home connection more precisely than IPv4. Good VPN apps either route IPv6 through the tunnel or block it while connected. A web proxy works at a different level. Your browser only talks to the proxy; the proxy server then contacts the site over whichever protocol it has. We saw both cases on 15 October 2026 on browserleaks.com/ip: through AnyProxy's Frankfurt region the IPv6 row read 'undefined', while through Singapore it showed a Singapore IPv6 address belonging to the proxy. In neither case did the test machine's own IPv6 appear in the page's IP rows. The same page's WebRTC row, however, still listed the test machine's own addresses, because WebRTC is not carried by a web proxy. So the honest summary: no IPv6 leak through page requests, but WebRTC is a separate gap.

In practice

IPv6 leak in the real world

An IPv6 leak happens when a VPN tunnels IPv4 traffic but the device still has a working IPv6 route, so anything reachable over IPv6 goes out directly. It is not a niche case: Google's own statistics show a large and growing share of users reaching it over IPv6. A VPN that does not handle IPv6 should block it; a web proxy is unaffected, because the browser only connects to the proxy.

Sources: Google — IPv6 statistics

We checked

IPv6 rows seen through two AnyProxy regions

BrowserLeaks What Is My IP through AnyProxy Frankfurt: Germany, Google LLC, IPv6 address undefined, WebRTC public IP rows from the test machine, addresses hidden

IP and IPv6 check on browserleaks.com/ip through AnyProxy

Partly worked · FR exit · 2026-10-15

IP location: Frankfurt am Main, Germany, Google LLC (AS396982). IPv6 Leak Test row shows 'undefined': the Frankfurt exit presented no IPv6 address. The WebRTC row on the same page still shows the test machine's own two public addresses.

BrowserLeaks What Is My IP through AnyProxy Singapore: Singapore, Google LLC, IPv6 row with Singapore flag, WebRTC rows from the test machine, addresses hidden

IP and IPv6 check on browserleaks.com/ip through AnyProxy

Partly worked · SG exit · 2026-10-15

IP location: Singapore, Google LLC (AS396982). The IPv6 Leak Test row shows a Singapore-flagged IPv6 address, so this exit reached the IPv6 test itself; the test machine's IPv6 did not appear there. The WebRTC row still shows the test machine's own addresses.

Questions about IPv6 leak

How do I check for an IPv6 leak?
Connect your VPN and open an IP-check page that shows IPv6. If it shows an IPv6 address from your own ISP, IPv6 is leaking.
Why does one region show IPv6 and another show none?
It depends on the proxy server's network, not yours. In our test the Singapore exit reached the IPv6 check over IPv6 and the Frankfurt exit did not. Either way, the address shown belongs to the proxy.
Should I turn IPv6 off?
Only if your VPN cannot protect it. A better fix is a VPN that tunnels IPv6 or blocks it while connected.

Related terms

VPNA VPN (virtual private network) is software that sends all of a device's network traffic through an encrypted connection to a provider's server, which then contacts websites on the device's behalf.DNS leakA DNS leak is when your device keeps asking its usual DNS server (often the ISP's) to look up site names while you think a VPN or proxy is handling your traffic, so the network still learns which sites you visit.WebRTC leakA WebRTC leak is when a website uses the browser's built-in calling technology (WebRTC) to discover your real public IP address, even though your normal page traffic goes through a proxy or VPN.IP addressAn IP address is the number that identifies a device or server on a network, so packets know where to go; every website you visit sees one for you.

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