Guide
IPv4 vs IPv6
The internet runs on two versions of the Internet Protocol. Here is how they differ, why there are two, and what it means for you.
Every device on the internet needs an IP address. IPv4, the original version, has been in use since 1981. IPv6 was designed in the 1990s because IPv4 was running out of addresses. Today both run side by side, and most devices speak both without you noticing.
The differences at a glance
| IPv4 | IPv6 | |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Number of addresses | About 4.3 billion | About 340 undecillion (3.4 × 1038) |
| Example | 203.0.113.42 | 2001:db8::42 |
| Notation | Four decimal numbers, 0–255 | Eight groups of hex digits |
| Sharing addresses | Common: many devices behind one address (NAT) | Rarely needed: every device can have its own |
| Automatic setup | Usually DHCP from the router | Devices can configure themselves (SLAAC) or use DHCPv6 |
Why IPv4 ran out
About 4.3 billion addresses sounded like plenty in 1981. By the 2000s, with computers, phones and servers everywhere, it wasn’t. In February 2011, IANA handed out its last free blocks of IPv4 addresses to the regional registries, which then ran out one after another.
The internet kept growing thanks to NAT (network address translation): your router uses one public IPv4 address for every device in your home. Many providers go further and share one public address between many customers. It works, but it makes some things harder, such as reaching a device at home from outside.
What IPv6 changes
- Practically unlimited addresses, so every device can have its own public address again.
- Simpler routing, with a streamlined packet header and no address translation in between.
- Self-configuration: devices can create their own address from the network prefix their router announces.
- Privacy addresses: modern systems use temporary IPv6 addresses that change regularly, so websites can’t follow one device by its address.
Reading an IPv6 address
An IPv6 address has eight groups of four hexadecimal digits: 2001:0db8:0000:0000:0000:ff00:0042:8329. Two rules make it shorter: leading zeros in a group can be dropped, and one run of all-zero groups can be replaced by ::. So the same address is written 2001:db8::ff00:42:8329.
Adoption today
IPv6 use differs a lot between countries and providers. Google’s statistics show that more than 40% of its users now reach it over IPv6. Websites and services almost always remain reachable over IPv4 too, so nothing breaks for people who don’t have IPv6 yet.
New to IP addresses? Start with what is an IP address?
Frequently asked questions
Do I have IPv6?
It depends on your internet provider, your router and your device. Most phones and computers support IPv6 today, and many providers enable it by default. Your router’s settings show whether it has an IPv6 address.
Why does IPLookr show an IPv4 address?
IPLookr can only see the address your browser used to reach it, and it is reached over IPv4. Your device may have an IPv6 address as well; your router or network settings show it.
Should I turn off IPv6?
Usually not. Modern systems handle both versions automatically, and turning IPv6 off can cause problems with some networks and services. Only do it to solve a specific problem.
Will IPv4 stop working?
Not any time soon. Most of the internet runs both versions side by side, and IPv4 addresses are reused and shared to keep it going. The two will coexist for many years.
Is IPv6 faster?
Sometimes slightly, because it can skip the address translation IPv4 networks need, but for everyday browsing the difference is rarely noticeable.