IPv4 vs IPv6: Differences, Formats and Examples
IPv4 and IPv6 are two versions of the addressing system used on the Internet. The easiest way to tell them apart is their punctuation: IPv4 addresses use dots, while IPv6 addresses use colons.
An IPv4 address looks like 203.0.113.24. An IPv6 address can look like 2001:db8::1. Both versions are in everyday use, and the same device or website can use both.
How do IPv4 and IPv6 compare?
| Characteristic | IPv4 | IPv6 |
|---|---|---|
| Example | 203.0.113.24 | 2001:db8::1 |
| Writing style | Four numbers separated by dots. | Groups of numbers and letters separated by colons. |
| Address supply | About 4.3 billion possible addresses. | Vastly more addresses than IPv4. |
| Use today | Still widely used. | Widely supported and becoming more common. |
IPv6 was created because the Internet outgrew the available supply of IPv4 addresses. It provides enough addresses for continued growth while doing the same basic job: helping traffic reach the right network. For a broader introduction, see IP address basics.
How is an IPv4 address formatted?
An IPv4 address has four numbers separated by dots. Each number must be from 0 through 255. For example, 203.0.113.24 is valid, but 203.0.113.256 is not because 256 is too large.
IPv4 has about 4.3 billion possible addresses. That was not enough for every modern device to have a separate public IPv4 address, so sharing is common. A phone, laptop, and television in one home can all appear to websites under the same public address.
Devices inside a home or office often also have addresses used only on that local network. Websites normally see the shared public address instead, so one IPv4 address does not necessarily mean one person or device.
How is an IPv6 address formatted?
An IPv6 address is normally written as eight groups separated by colons. The groups use the digits 0 through 9 and the letters a through f. A fully written example is 2001:0db8:0000:0000:0000:0000:0000:0001.
IPv6 addresses can be shortened. Leading zeros in a group may be left out, and one continuous run of zero groups may be replaced with ::. That turns the full example above into 2001:db8::1. The :: shortcut can appear only once in an address.
The much larger IPv6 address supply makes widespread public-address sharing unnecessary. This does not make IPv4 disappear, however. Networks and services continue to support both versions while both remain in everyday use.
How does dual-stack use IPv4 and IPv6 together?
A dual-stack device or network supports both IPv4 and IPv6. It can use IPv6 when the destination and network support it, and IPv4 when that is the available option. The device and network normally make this choice automatically.
For example, the same phone may connect to one website over IPv6 and another over IPv4. A website may also receive an IPv6 request from a visitor at one time and an IPv4 request from the same visitor later. The two addresses are different, even though the device or Internet connection may be the same.
What do IPv4 and IPv6 mean for IP lookups?
IP Lens can look up either version. A lookup can describe the network associated with an address and provide an estimated location, but it normally cannot identify a particular person or device.
- One public IPv4 address may be shared by several devices or customers.
- One device can have both an IPv4 address and an IPv6 address.
- An address can change over time, so a new address does not automatically mean a new user.
- IPv4 and IPv6 results can differ because they use separate address blocks.
Treat an IP address as one clue rather than proof of identity or an exact physical location.
Common IPv4 and IPv6 questions
Which version am I using?
Open the What is my IP address? section. Dots mean IPv4; colons mean IPv6.
Is IPv6 always faster?
No. Speed depends on the networks and routes involved. Either version can be faster for a particular connection.
Is IPv6 automatically safer?
No. Both versions still need normal protections such as a firewall, secure settings, and up-to-date software.
Can I convert an IPv4 address to IPv6?
No. There is no general one-to-one conversion. A device or service may have both addresses, but they are separate and should be looked up separately.
Do I need both IPv4 and IPv6?
Most people do not need to choose. Their device and Internet provider handle the available versions. Websites and network operators commonly support both while IPv4 remains in use.