Side by side
IPv4vsIPv6
What is the difference between IPv4 and IPv6?
Updated 2 min read7 differences
In short
IPv4 uses 32-bit addresses, allowing about 4.3 billion of them, while IPv6 uses 128-bit addresses, enough for every device to have its own public address.
IPv4
Internet Protocol version 4
IPv4 is the internet's original addressing system, using 32-bit addresses written as four numbers such as 192.168.1.10, allowing about 4.3 billion addresses.
Read the page on IPv4IPv6
Internet Protocol version 6
IPv6 is the newest version of the Internet Protocol, using 128-bit addresses that give every device a unique address and replace the exhausted IPv4 pool.
Read the page on IPv6IPv4 and IPv6 compared
| Aspect | IPv4 | IPv6 |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Number of addresses | About 4.3 billion | Practically unlimited |
| Notation | Dotted decimal: 192.168.1.10 | Hexadecimal groups: 2001:db8::1 |
| NAT | Widely needed | Not needed |
| Address setup | DHCP or manual | Automatic (SLAAC), DHCPv6 or manual |
| Standardized | 1981 | The 1990s |
| Today | Still dominant in many networks | Growing; common on mobile and large sites |
The difference, explained
IPv4 was defined in 1981, when nobody imagined billions of phones and connected devices. Its 32-bit addresses give about 4.3 billion possibilities, and the global pool of free addresses ran out in 2011. The internet kept growing mainly through NAT, which lets many devices share one public address, at the cost of extra complexity.
IPv6, first standardized in the 1990s, uses 128-bit addresses written as eight groups of hexadecimal numbers, such as 2001:db8:85a3::8a2e:370:7334, where :: shortens a run of zeros. The address space is so large that NAT becomes unnecessary, devices can configure their own addresses automatically, and the packet header is simpler for routers to process.
The two are not directly compatible, so networks run both side by side, which is called dual stack, and use translation where needed. Adoption has grown steadily: a large share of mobile networks and home connections now support IPv6, and big websites serve it by default, while many corporate networks and older systems still rely on IPv4.
A common misconception is that IPv6 is just IPv4 with longer addresses. Address configuration, neighbor discovery and the header format all changed, and firewall rules must be written for IPv6 too, because devices with public IPv6 addresses aren't hidden behind NAT.
Which one should you use?
Choose IPv4 when…
- You work with older systems or networks that only support IPv4.
- You configure internal networks where private IPv4 ranges suffice.
- A service or partner you depend on is IPv4-only.
Choose IPv6 when…
- You deploy new networks, mobile services or large fleets of devices.
- You want to avoid NAT and the cost of public IPv4 addresses.
- You want your service reachable on modern IPv6-only networks.
Readers ask
Why do we need IPv6?
Because IPv4's roughly 4.3 billion addresses ran out. IPv6 provides enough addresses for every device and removes the need for workarounds such as NAT.
Can IPv4 and IPv6 talk to each other?
Not directly. Networks run both protocols side by side, and translation mechanisms such as NAT64 let IPv6-only devices reach IPv4 services.
Is IPv6 more secure than IPv4?
Not automatically. IPv6 was designed with IPsec support, but security depends on configuration; without NAT, firewalls must explicitly protect devices with public IPv6 addresses.