IPv6 is officially mainstream now. Google recorded 50.1% of its traffic over IPv6 in March 2025, and global adoption has since blown past 45%. France is leading the charge at 80–85%, the U.S. crossed 50%, and Vietnam hit 67.68%. India and Malaysia are also in the top tier. The transition isn't coming—it's here.
But here's the catch most people don't realize: IPv6 has serious privacy baggage.
Your device used to wear a name tag
Early IPv6 addresses were built using EUI-64, which took your network adapter's MAC address—a unique 12-digit hardware fingerprint—and folded it directly into your IPv6 address. Same device, same suffix, everywhere. Your laptop carried that identifier from your home network to the coffee shop to the hotel Wi-Fi, making it trivially easy to track you across networks.
Privacy extensions (RFC 8981) largely fixed that by generating random, temporary addresses that rotate regularly. Most modern operating systems have this enabled by default now.
Your house still has a permanent label
The bigger issue today is your network prefix. Your ISP assigns your home a prefix that can sit unchanged for weeks or months. Because IPv6 has no address scarcity, there's no pressure to rotate it. That single prefix effectively becomes a permanent label for your household. Anyone tracking your traffic doesn't need to know which specific device you're using—they just need to know which house it came from.
VPNs aren't always the safety net you think
A 2025 study of 129,000 VPN users found that IPv4-only VPNs leak IPv6 traffic to the ISP, exposing real IPv6 addresses for 5% to 57% of their visitors. Even dual-stack VPNs often prioritize IPv4 over IPv6 due to how address selection rules work. In other words, you might be paying for privacy while your IPv6 address is quietly leaking out the back door.
What you can do about it
- Check if Privacy Extensions are enabled – Windows, macOS, and most Linux distros have them on by default. If yours doesn't, turn them on.
- Verify your VPN's IPv6 support – Not all VPNs handle IPv6 properly. Look for one with explicit IPv6 leak protection.
- Consider DHCPv6 over SLAAC – The NSA recommends using DHCPv6 for address assignment rather than SLAAC, as it gives network operators more control.
- Monitor your prefix rotation – If your ISP keeps the same prefix for months, it's worth asking if they can rotate it more frequently.
IPv6 is the future, and that future is already here. Just make sure you're not leaving your privacy behind in the transition.