The differences at a glance
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Number of addresses | About 4.3 billion | About 3.4 × 10³⁸ |
| Format | 192.168.1.10 | 2001:db8:85a3::8a2e:370:7334 |
| Sharing addresses | NAT and CGNAT common | Each device can have a global address |
| Address setup | DHCP or manual | Automatic (SLAAC) or DHCPv6 |
| Support | Universal | Widespread, but depends on ISP and router |
Why IPv6 exists
IPv4 was designed in the early 1980s, when 4.3 billion addresses seemed plenty. With phones, laptops, TVs and billions of other devices online, the central pool of IPv4 addresses was exhausted in 2011, and regional registries have since run out of or rationed their own supplies.
NAT stretched IPv4 by letting a whole household, and with CGNAT many households, share one public address. IPv6 removes the shortage altogether, so devices can be reached directly (subject to the router's firewall) without port forwarding.
Reading an IPv6 address
An IPv6 address is eight groups of four hexadecimal digits. Leading zeros in a group can be dropped, and one run of all-zero groups can be replaced by a double colon. So 2001:0db8:0000:0000:0000:0000:0000:0001 is written 2001:db8::1. The first half usually identifies the network (your ISP assigns a prefix to your router); the second half identifies the device.
Speed, gaming and security
Neither version is faster by design. What matters is the path traffic takes. IPv6 can help when it avoids a congested CGNAT gateway and can hurt when an ISP's IPv6 routes are longer. Browsers use “Happy Eyeballs”, trying both and using whichever connects first, so you rarely feel a difference.
On security, IPv6 devices having public addresses doesn't make them exposed: home routers block unsolicited incoming IPv6 traffic by default, just as NAT effectively does for IPv4. Keep the router firewall on.
Do you have IPv6?
Google reports that close to half of its users worldwide now reach it over IPv6, but support varies widely between countries and ISPs. Run the IPv6 test to see whether your connection works over IPv4, IPv6 or both, and which addresses you have. If you'd like IPv6, check that it's enabled in your router (often “IPv6” or “Internet → IPv6” settings) and ask your ISP whether your plan supports it.
Common questions
Is IPv6 faster than IPv4?
Not inherently. Speed depends on the route and the networks in between. IPv6 can be slightly faster where it avoids carrier-grade NAT, and slightly slower where an ISP's IPv6 routing is less optimised. For most people the difference is too small to notice.
Should I turn off IPv6?
Generally no. Modern operating systems prefer whichever works better and fall back automatically. Disabling IPv6 is only worth trying as a temporary test if a specific site or app fails over IPv6.
Why does my connection not have IPv6?
Your ISP must support it and your router must have it enabled. Many ISPs, particularly in countries still rolling it out, offer IPv4 only on some plans or equipment.