IPv6 is the current version of the Internet Protocol — the system that gives every device on the internet an address. It exists because the old system, IPv4, ran out of addresses. IPv4 offers about 4.3 billion; IPv6 offers roughly 340 undecillion, a number with 38 digits.
For most people the honest answer to “should I use it?” is: you probably already are, and you should leave it on — with one specific exception involving VPNs that’s worth understanding before you trust your tunnel.
Key Takeaway:
IPv6 isn’t an upgrade you feel. The one thing that genuinely matters day to day is that many VPNs don’t tunnel it — so IPv6 traffic can slip past your VPN and expose your real address while the app still says “Connected.”
Why IPv6 Exists
IPv4 addresses are 32 bits long, which caps the total at about 4.3 billion. In the 1980s that seemed limitless. Then everyone got a phone, a laptop, a TV and a doorbell, and the pool ran dry — the central allocation of new IPv4 blocks was exhausted years ago.
Two things kept IPv4 alive past its expiry date. NAT let entire households share one public address, and CGNAT extended the same trick to whole neighbourhoods at the ISP level. Both work, and both add complexity that IPv6 simply removes by having enough addresses for everyone.
IPv4 vs IPv6
| IPv4 | IPv6 | |
|---|---|---|
| Length | 32-bit | 128-bit |
| Total addresses | ~4.3 billion | ~340 undecillion |
| Looks like | 192.168.1.1 | 2001:db8:85a3::8a2e:370:7334 |
| NAT | Required in practice | Not needed |
| Configuration | DHCP | Devices can self-assign |
| VPN support | Universal | ⚠️ Inconsistent |
How to Read an IPv6 Address
They look intimidating, but the rules are simple. An IPv6 address is eight groups of four hexadecimal digits separated by colons:
2001:0db8:85a3:0000:0000:8a2e:0370:7334
Two shortcuts make them readable:
- Drop leading zeros in any group —
0db8becomesdb8. - Replace one run of all-zero groups with
::— the two zero groups above collapse away.
Which gives 2001:db8:85a3::8a2e:370:7334. You can only use :: once per address, otherwise there’d be no way to tell how many groups it stands in for.
The first half typically identifies your network (the prefix your ISP assigned), and the second half identifies the device on it — conceptually similar to subnetting in IPv4.
What Actually Changes for You
Day to day, almost nothing. Websites load the same way, and your device quietly picks whichever protocol works better for each connection — trying both and preferring the faster response.
That mechanism is also why a broken IPv6 setup is worse than none at all: your device keeps attempting a route that fails, then falls back, adding delay to everything. If your connection feels inexplicably sluggish, IPv6 is worth testing as a cause — see connectivity troubleshooting.
The Privacy Side Nobody Mentions
This is where IPv6 gets genuinely interesting, and it cuts both ways.
No NAT means no hiding in the crowd. On IPv4, every device in your home shares one public address, so a website can’t distinguish your laptop from your phone by IP alone. On IPv6 each device can have its own globally routable address — which is more transparent, and potentially more identifying.
Early IPv6 embedded your hardware address. The original auto-configuration scheme derived the device portion of the address from the network card’s MAC address. That meant a permanent, hardware-tied identifier travelling with you across every network you joined — a tracking dream. It was recognised as a problem and fixed: modern operating systems use privacy extensions, generating temporary randomised addresses that rotate periodically. Windows, macOS, iOS and Android all enable this by default now.
Your network prefix is still fairly stable. Even with rotating device portions, the prefix your ISP delegates tends to persist. That identifies your household, much as a static IPv4 address would. See what your IP reveals.
And the security point from NAT firewalls applies here too: without NAT, the incidental “no route inbound” protection disappears, and you’re relying on your router’s actual firewall. Most enable IPv6 filtering by default — but it’s now a setting rather than a side effect.
⚠️ IPv6 and VPN Leaks
This is the one practical issue worth acting on.
Plenty of VPNs tunnel only IPv4. If your connection also has IPv6 and the VPN doesn’t handle it, IPv6 traffic leaves your device outside the tunnel entirely. Sites reached over IPv6 see your real address. Your VPN app reports “Connected” throughout, because from its perspective nothing is wrong — it simply never took responsibility for that traffic.
Test for it: connect your VPN, then run the VPN Leak Test. If an IPv6 address appears that belongs to your ISP rather than the VPN, you’re leaking. The same failure pattern applies to DNS leaks — full method in How to Check If Your VPN Is Working.
Three ways to resolve it, best first:
- Use a VPN that tunnels IPv6 properly, or one that blocks IPv6 outright while connected. Either is a correct answer.
- Enable IPv6 leak protection in your VPN’s settings if it offers it.
- Disable IPv6 on the device while using the VPN. Effective, but you lose IPv6 everywhere.
🔒 Providers That Handle IPv6 Properly
A provider that neither tunnels nor blocks IPv6 is leaving a hole open by default:
Should You Enable IPv6?
Leave it on if:
- Your ISP supports it and everything works — you’ll get direct routes to IPv6-native services
- You’re behind CGNAT and want a genuinely reachable address
- You don’t use a VPN, or yours handles IPv6 correctly
Consider turning it off if:
- Your VPN leaks IPv6 and you’re not switching providers
- Your ISP’s implementation is unstable and causing slow or failed connections
- You’re isolating a network fault and need to rule it out
How to Check and Change It
To check: open What Is My IP. If an address containing colons appears, you have IPv6. From a terminal, run ipconfig on Windows or ifconfig on Mac and Linux, and look for an address beginning 2001: or similar.
| Platform | Where to Toggle It |
|---|---|
| Windows | Network Connections → adapter → Properties → untick “Internet Protocol Version 6” |
| macOS | System Settings → Network → Details → TCP/IP → Configure IPv6 → Off |
| Router | Admin panel → WAN or IPv6 section — disables it for the whole network |
| iOS / Android | Not user-configurable — handle it at the router or in the VPN app |
Frequently Asked Questions
Do I need to do anything to start using IPv6?
No. If your ISP and router support it, your devices use it automatically. Most people have had it for years without noticing.
Is IPv6 faster than IPv4?
Marginally, for services that are IPv6-native, because there’s no NAT translation in the path. The difference is rarely perceptible. A badly configured IPv6 setup, however, is noticeably slower than none.
Is IPv6 more secure?
Not inherently. Encryption support was part of the design, but it isn’t automatic — and losing NAT removes a layer of incidental inbound protection. Security depends on your router’s firewall, exactly as it should.
Can I be tracked more easily on IPv6?
Potentially, since devices can have individual public addresses rather than hiding behind one shared one. Privacy extensions rotate the device portion to counter this, and they’re on by default in modern systems. Your network prefix remains reasonably stable.
Will disabling IPv6 break anything?
Almost certainly not today — the internet still works fully over IPv4. Some local features like network discovery may behave differently, and long term this will become a worse trade-off.
Does IPv6 fix CGNAT?
Yes, that’s precisely what it’s for. With enough addresses, ISPs don’t need to share one among many customers — so you can host services and forward ports again. See What Is CGNAT?
Why does my IPv6 address keep changing?
That’s privacy extensions doing their job — temporary addresses rotate deliberately to make you harder to track across sessions. It’s a feature, not a fault.
Can two devices have the same IPv6 address?
They shouldn’t, and there are enough addresses that collisions are effectively impossible. Devices also run duplicate address detection before using one. See can two devices share an IP.