IPExposed
Privacy Guide

What Is IPv6 and Why Does It Matter for Privacy?

5 min read · Updated April 2026

Here is the short answer: Internet Protocol version 6 (IPv6) is the newer format for IP addresses that is gradually replacing the older Internet Protocol version 4 (IPv4). Most people have both types active on their connection without realizing it. The privacy problem is that many commercial Virtual Private Networks (VPNs) only create a tunnel for IPv4 traffic — leaving your real IPv6 address fully exposed to every website you visit, even while your VPN appears to be active.

What Is IPv6?

The internet's addressing system is governed by the Internet Protocol (IP). Every device connected to the internet needs a unique address so that data can be routed to the correct destination — the same way every postal address is unique so that mail arrives at the right building.

The original addressing format, Internet Protocol version 4 (IPv4), represents addresses as four groups of numbers from 0 to 255, separated by dots. An IPv4 address looks like this: 192.0.2.1. The technical specification for IPv4 has been in use since the 1980s.

Internet Protocol version 6 (IPv6) uses a different format: eight groups of four hexadecimal characters separated by colons. An IPv6 address looks like this: 2001:0db8:85a3:0000:0000:8a2e:0370:7334, which is often shortened to 2001:db8:85a3::8a2e:370:7334. The full specification is defined in RFC 8200 at the Internet Engineering Task Force (IETF).

Why Does IPv6 Exist?

IPv4 can accommodate approximately 4.3 billion unique addresses. When the protocol was designed in the early 1980s, that seemed more than enough. It was not.

The Internet Assigned Numbers Authority (IANA) exhausted the last available IPv4 address blocks in 2011. You can see the IANA IPv4 address space registry and its current allocation status. For years, the internet has managed the shortage through Network Address Translation (NAT) — the technique that lets an entire household share a single public IPv4 address across many devices.

IPv6 solves the shortage problem by using 128-bit addresses instead of 32-bit ones. This allows for approximately 340 undecillion unique addresses — a number so large it is effectively inexhaustible for any realistic scale of internet use. IPv6 also has technical advantages: each device can have its own globally unique address rather than sharing one through NAT, which simplifies certain network configurations.

The transition to IPv6 has been gradual. As of 2024, most major internet service providers offer dual-stack connectivity — meaning your home connection has both an IPv4 address and an IPv6 address active simultaneously.

How Do I Know If I Am Using IPv6?

Check your connection here — we detect and display both your IPv4 and IPv6 addresses if both are active on your current network. If you see an IPv6 address listed, your Internet Service Provider (ISP) has assigned you one. If you only see an IPv4 address, you are either on a network that has not yet deployed IPv6, or your ISP provides IPv4 only.

Many mobile networks and modern home broadband connections are dual-stack by default. Coffee shops, airports, and hotel networks often use IPv4-only configurations because they rely on older equipment.

The IPv6 Leak Problem With VPNs

This is where IPv6 becomes a real privacy issue rather than just a technical curiosity.

When you connect to a VPN, the software creates an encrypted tunnel between your device and the VPN server. Any traffic that travels through this tunnel appears to originate from the VPN server's IP address, not your real one. This is the core privacy protection a VPN provides.

The problem is that many VPN applications are designed around IPv4 tunneling. When your device has both an IPv4 address and an IPv6 address — a dual-stack configuration — the VPN may only route IPv4 traffic through its encrypted tunnel. Your device continues to send IPv6 traffic directly to its destination, bypassing the VPN entirely.

This is called an IPv6 leak. The website you visit receives two signals: the VPN's IPv4 address (which suggests you are in, say, Amsterdam) and your real IPv6 address (which resolves directly to your home ISP and approximate city). The VPN's location masking is completely undermined.

The issue is not theoretical. Cloudflare's research on IPv6 connectivity and deployment notes that dual-stack is increasingly the default — meaning more users are affected than realize it. Some VPN applications address this by blocking all IPv6 traffic when the VPN is active (so only IPv4 traffic, protected by the tunnel, goes through). Others support full IPv6 tunneling. Many do neither, silently leaking IPv6 on dual-stack connections.

So What Does This Mean for You?

If you use a VPN specifically to keep your browsing private — from your ISP, from advertisers, or from the sites you visit — an IPv6 leak means you are paying for protection you may not actually have.

Every website you visit while your VPN is "on" can still receive your real IPv6 address if it is not being tunneled. That IPv6 address is typically more stable and uniquely identifying than your IPv4 address, because many ISPs assign static IPv6 prefixes to home connections that persist for months or years.

The steps to protect yourself: verify that your VPN application explicitly states it handles IPv6 (either by tunneling it or blocking it when the VPN is active), and check your connection on a tool that shows both address types so you can confirm whether your real IPv6 is visible.

Sources