If you've ever checked your connection details and seen two completely different-looking addresses, you've met IPv4 and IPv6 — the old and new versions of the system that gives every device on the internet an address. The internet has spent more than a decade quietly migrating from one to the other. Here's what's actually going on, in plain terms.
The problem IPv4 ran into
IPv4 is the original addressing scheme, and it's the one most people picture when they think of an IP address:
198.51.100.27
Four numbers, each 0–255. That format allows about 4.3 billion unique addresses. In the early 1980s that seemed limitless. Then came home broadband, smartphones, smart TVs, watches, doorbells, and an internet of billions of devices. The world ran out of fresh IPv4 addresses years ago.
Clever workarounds kept IPv4 alive — chiefly NAT, which lets a whole household share one public address (we cover that in public vs private IP addresses). But these are patches over a fundamental shortage.
What IPv6 changes
IPv6 is the long-term fix. Instead of 32-bit addresses it uses 128-bit ones, written as eight groups of hexadecimal digits:
2001:0db8:85a3:0000:0000:8a2e:0370:7334
The number of possible IPv6 addresses is so large it's hard to convey — roughly 340 undecillion, or enough to give every grain of sand on Earth billions of addresses each. The practical point is simple: we will never run out.
IPv6 addresses are often shortened by dropping leading zeros and collapsing runs of zeros with ::, so the example above becomes:
2001:db8:85a3::8a2e:370:7334
That's the same address, just written compactly.
Why the switch is so slow
A new addressing system that's been ready for years still isn't universal — why? Because the entire internet, every router, server, and provider, has to support it, and IPv4 still works well enough thanks to NAT. There's no single switch-off date; instead, the two run side by side in a long transition.
Most modern connections use dual stack: your device gets both an IPv4 and an IPv6 address and uses whichever the destination supports. That's why you might see both when you check your setup — it's not an error, it's your connection being ready for either world.
Does IPv6 affect your privacy?
A little, and it's worth knowing. Under IPv4 with NAT, all your home devices share one public address, which blurs them together from the outside. IPv6 can give each device its own globally routable address, which in theory makes individual devices more directly identifiable.
In practice, this is mitigated by privacy extensions — a feature that makes your device generate temporary, rotating IPv6 addresses for outgoing connections rather than using one fixed address tied to your hardware. Most operating systems enable this by default. So the privacy difference is smaller than it first appears, but it's a real reason the details matter.
Is IPv6 faster?
Not inherently. IPv6 can sometimes feel slightly faster because it avoids some of the NAT processing IPv4 relies on, and because it allows more direct device-to-device connections. But for everyday browsing the difference is negligible. Don't switch for speed; the migration is about address supply, not performance.
Do you need to do anything?
For almost everyone, no. Your provider, your router, and your devices handle the IPv4/IPv6 decision automatically. You don't choose, and you don't configure anything. The main reasons to care are understanding what you see when you check your connection, and knowing that an IPv6 address is just as valid an identifier as an IPv4 one when you're thinking about privacy.
A few situations where it does come up:
- Some VPNs only tunnel IPv4 and can leak your real IPv6 address. If you rely on a VPN, it's worth confirming it handles IPv6 — our guide to checking if your VPN is working covers leak testing.
- Running servers or self-hosting may require understanding both, since reachability differs.
- Older hardware occasionally doesn't support IPv6 cleanly, which can cause odd connection issues.
How to see which you're using
Open the Check My Setup homepage and look at the address it reports. If you see a long, colon-separated address, you're on IPv6 (at least in part). If it's four dotted numbers, you're seeing IPv4. Many people see both, which simply means dual stack is doing its job.
The takeaway
IPv4 ran out of addresses; IPv6 provides effectively unlimited ones, and the internet is in a long, gradual switch from the first to the second. For day-to-day use you don't need to do anything — but knowing the difference helps you read your own connection details and understand the small privacy nuances each version brings.
See which version your connection is using right now on the homepage.