IPv4 uses 32-bit addresses and supports about 4.3 billion unique addresses. IPv6 uses 128-bit addresses and provides an enormously larger address space. Both versions are currently used across the Internet.
Every device that communicates over the Internet needs an Internet Protocol address. For decades, most Internet traffic used Internet Protocol version 4, better known as IPv4. As the number of connected devices grew, the supply of available IPv4 addresses became insufficient. IPv6 was developed to provide far more addresses and support the Internet's continued growth.
IPv6 is the newer standard, but IPv4 has not disappeared. Internet providers, websites, phones, routers and computers often support both versions at the same time.
IPv4 vs IPv6 comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Typical format | Four decimal groups separated by dots | Hexadecimal groups separated by colons |
| Address capacity | About 4.3 billion addresses | Approximately 3.4 × 1038 addresses |
| Network Address Translation | Commonly used to share public addresses | Usually unnecessary for address conservation |
| Address configuration | Manual configuration or DHCP is common | Supports automatic address configuration |
| Current use | Still widely supported | Growing and designed for long-term expansion |
What is IPv4?
IPv4 is the fourth version of the Internet Protocol. It uses a 32-bit address divided into four decimal numbers. Each number ranges from 0 to 255 and the groups are separated by periods.
A 32-bit system provides roughly 4.3 billion possible addresses. That sounded enormous when IPv4 was designed, but today billions of phones, computers, servers, smart TVs, sensors and other devices connect to networks.
To extend the useful life of IPv4, many networks use Network Address Translation, or NAT. NAT lets several devices on a private network share a single public IPv4 address. This is why your phone and computer may have different private addresses at home while websites see the same public address for both devices.
What is IPv6?
IPv6 is the newer Internet Protocol standard. It uses 128-bit addresses written with hexadecimal characters and colons. Because its address space is vastly larger, IPv6 can provide unique addresses for an extraordinary number of devices and networks.
IPv6 also simplifies some parts of network configuration and reduces the need to share addresses purely because of address scarcity. An IPv6 address may look more complicated, but devices and network software handle it automatically. Most people never need to type one manually.
How IPv6 address compression works
An IPv6 address contains eight 16-bit hexadecimal groups.
Leading zeros inside a group can be omitted, and one
continuous sequence of all-zero groups can be replaced
by ::. The double colon can appear only once
because the missing groups must remain unambiguous.
2001:db8::1
Both lines represent the same address. The first keeps
every group and leading zero; the second uses the
compressed form. The 2001:db8::/32 prefix
is reserved for documentation, so it is appropriate for
examples and should not be treated as a reachable public
target. The formal IPv6 address rules are defined in
RFC 4291.
Common special-purpose address examples
-
IPv4 private:
10.0.0.0/8,172.16.0.0/12and192.168.0.0/16. -
IPv4 loopback:
127.0.0.0/8, including127.0.0.1. -
IPv6 loopback:
::1. -
IPv6 link-local:
fe80::/10, used for communication on the local link. -
IPv6 unique local:
fc00::/7, intended for local communication rather than ordinary global routing.
What are the main differences?
1. Address size and format
IPv4 addresses are shorter and use decimal numbers, while IPv6 addresses are longer and use hexadecimal characters. The longer IPv6 format creates a much larger pool of possible addresses.
2. Available address space
IPv4 address scarcity led providers and organizations to reuse addresses through NAT. IPv6 was designed with enough capacity to support continued growth without depending on address sharing for conservation.
3. Network configuration
Both protocols can use automatic configuration. IPv6 adds Stateless Address Autoconfiguration, which allows a device to create an address using information announced by the local router. Managed IPv6 networks may also use DHCPv6.
4. Broadcast and multicast
IPv4 networks can use broadcast traffic to send data to every device on a local network. IPv6 does not use broadcast in the same way. It relies on multicast and anycast methods to communicate with relevant devices more efficiently.
5. Prefixes and subnet notation
Both versions use slash prefixes, but the numbers
describe different address lengths. An IPv4
/24 fixes 24 of 32 bits and leaves 8 host
bits. A typical IPv6 LAN uses a /64,
fixing the first 64 of 128 bits and leaving a 64-bit
interface identifier. The same slash number must not
be interpreted as the same network size across both
protocols.
Use the IPv4 and IPv6
Subnet/CIDR Calculator to calculate prefix boundaries and
address ranges. For IPv6, try /64 for a typical LAN,
/127 for a point-to-point link or /128 for a single address.
6. DNS record types
DNS normally publishes IPv4 destinations in A records and IPv6 destinations in AAAA records. A domain can publish either type or both. Use the DNS Lookup to compare the A and AAAA answers for a domain without assuming that both routes are reachable from every network.
Is IPv6 faster than IPv4?
IPv6 is not automatically faster. Real-world performance depends on your Internet provider, the destination server, routing quality, network equipment and connection conditions. One protocol may be slightly faster on a particular route, while the other may perform better somewhere else.
Modern devices usually test available connections and use the route expected to work best. You normally do not need to select the protocol yourself.
Is IPv6 more secure?
Both IPv4 and IPv6 can be secure when configured correctly. IPv6 supports modern protocol features, but an IPv6 address alone does not protect a device. Firewalls, software updates, secure router settings and careful network administration remain important with either version.
NAT is sometimes mistaken for a security system. Although it can prevent some unsolicited connections as a side effect, it does not replace a firewall. IPv6 networks should also use properly configured firewall rules.
Can IPv4 and IPv6 work together?
Yes. A common setup called dual stack allows a device, router or website to support IPv4 and IPv6 simultaneously. When both versions are available, the operating system and browser decide which connection to use.
IPv4 and IPv6 are separate protocols and do not communicate directly without transition technology. Dual stack, tunnels and translation systems help maintain compatibility while the Internet continues adopting IPv6.
How a device chooses between IPv4 and IPv6
When DNS returns both A and AAAA records, modern connection software can evaluate both address families and try a usable route without making the person choose manually. The approach commonly called Happy Eyeballs is designed to reduce delays when one family is configured but performs poorly. Its behavior is described in RFC 8305.
This does not mean the two protocols merge. The selected connection still uses either IPv4 or IPv6. Results can differ between websites because one destination may publish only A records, only AAAA records, or use different routes for each family.
Dual stack, CGNAT, NAT64 and DNS64
- Dual stack: the device and network support IPv4 and IPv6 at the same time.
- CGNAT: a provider shares public IPv4 capacity among multiple customers.
- DNS64: a DNS resolver can synthesize IPv6 answers from IPv4-only destination data for a compatible network.
- NAT64: a translator allows an IPv6 client to reach an IPv4 service.
- Tunneling: one protocol is carried through another network when native connectivity is unavailable.
These mechanisms explain why a phone can work normally even when an app displays only IPv6, or why a router's WAN IPv4 address can differ from the public IPv4 visible to a website.
Why do I have two IP addresses?
If your Internet provider and device support dual stack, you may have a public IPv4 address and one or more IPv6 addresses. This is normal. The IPv4 address connects you to services that depend on IPv4, while IPv6 lets you reach services over the newer protocol.
Your public addresses are different from private or local addresses assigned inside your home or workplace network. Changing from Wi-Fi to mobile data can also change the public address that websites see. Read our public vs private IP guide for a complete explanation.
Does IPv6 expose your exact identity or location?
No IP address normally reveals an exact home address or proves who was using a connection. An IPv6 prefix can provide network-provider and approximate routing context, but location databases can be wrong. Devices may also create temporary IPv6 addresses to make long-term correlation more difficult, as described in RFC 8981.
Temporary addressing does not make traffic anonymous. Websites can use accounts, cookies and other browser or application signals, and a VPN changes the visible route without changing every identifier.
A reproducible IPv4 and IPv6 check
- Open the My IP checker and record the address type displayed on the current connection.
- Use the DNS Lookup to query a domain's A record, then repeat with AAAA.
- Switch between Wi-Fi and mobile data, reload the checker and compare the address family.
- If you use a VPN, repeat once with it enabled and once without it to identify which route changes.
Finding an AAAA record proves that the domain publishes an IPv6 destination; it does not prove that your current network reached the site over IPv6. Likewise, seeing a local IPv6 address does not guarantee complete end-to-end IPv6 connectivity.
Visit the My IP checker to see your current public IP address and whether the detected connection uses IPv4 or IPv6.
Should you use IPv4 or IPv6?
For most people, the best option is to leave both protocols enabled and let the device and network choose automatically. IPv4 remains necessary for compatibility with many services, while IPv6 provides the address capacity needed for the Internet's future.
Disabling IPv6 without a specific technical reason can cause slower connections or prevent access to services on networks that expect it. If you are troubleshooting a connection, document your current settings before changing them and restore the original configuration after testing.