IPv4 vs IPv6: What's the Difference?
IPv4 and IPv6 are two versions of the internet's addressing system, the numbers that identify every device online. IPv4 uses 32-bit addresses written like 203.0.113.10, allowing about 4.3 billion unique addresses, which the internet has run out of. IPv6 uses 128-bit addresses written like 2001:db8::1, providing a practically unlimited supply. Both still run side by side today, and most modern networks support both, so websites and devices work whether they use IPv4, IPv6, or both.
- IPv4
- 32-bit addresses, about 4.3 billion total, e.g. 203.0.113.10
- IPv6
- 128-bit addresses, roughly 340 undecillion total, e.g. 2001:db8::1
- Why IPv6 exists
- IPv4 addresses were officially exhausted at the top level (IANA, 2011)
- DNS records
- IPv4 uses A records; IPv6 uses AAAA records (MDN/Google)
- Coexistence
- Most networks run dual-stack, supporting both at once
- Not interchangeable
- IPv4-only and IPv6-only hosts need translation to communicate
What an IP address is #
Every device connected to the internet, from a phone to the server hosting a website, needs an IP address, a numeric label that lets data find its way to the right place, much like a postal address. IPv4 and IPv6 are simply two formats for those addresses. IPv4 is the original, in use since the early 1980s, written as four numbers separated by dots. IPv6 is its successor, designed to solve a problem IPv4's creators never anticipated: running out of addresses. When you type a domain name, DNS translates it into one of these IP addresses so your request reaches the correct server, a lookup our /services/domains-dns-email team manages for client sites. Understanding the two formats matters because the internet is in the middle of a decades-long transition from one to the other, running both at once, and occasional connectivity quirks trace back to how a network handles each. Both formats do the same fundamental job; they differ mainly in how many addresses they can express and how they are written.
How IPv4 works and why it ran out #
IPv4 uses 32-bit addresses, written as four numbers from 0 to 255 separated by dots, such as 203.0.113.10. That 32-bit design allows roughly 4.3 billion unique addresses, an amount that seemed limitless in the early 1980s when only a handful of computers were networked. The explosion of the internet, then smartphones, then billions of connected devices, exhausted that pool; the global authority IANA allocated its last large blocks in 2011. The internet survived on IPv4 through clever workarounds, chiefly Network Address Translation, or NAT, which lets many devices behind a single router share one public IPv4 address. This is why your home network's dozen gadgets appear to the outside world as one address. NAT bought time but adds complexity and breaks some direct connections. IPv4 is not going away soon, most websites still have an IPv4 address, but its scarcity is real, and buying additional IPv4 addresses now costs money on a secondary market, which is one reason IPv6 exists.
How IPv6 solves the problem #
IPv6 uses 128-bit addresses, quadrupling the bit length and expanding the address space to a number so large, roughly 340 undecillion, that it is effectively inexhaustible for any foreseeable future. There are enough IPv6 addresses to assign trillions to every person on Earth many times over. Addresses are written as eight groups of hexadecimal digits separated by colons, such as 2001:0db8:85a3:0000:0000:8a2e:0370:7334, with rules that let you shorten them by collapsing long runs of zeros, giving the compact 2001:db8:85a3::8a2e:370:7334. Beyond sheer quantity, IPv6 was designed to remove the need for NAT, letting every device have its own unique public address again, which simplifies direct connections and can improve performance for some real-time and peer-to-peer applications. It also built in features that were add-ons in IPv4. The catch is that IPv6 is not backward compatible: an IPv6-only device cannot talk directly to an IPv4-only device without translation, which is the main reason the transition has taken so long and why dual-stack networks exist.
The two address formats side by side #
Seeing both formats together, along with the DNS records that point a domain at each, makes the difference concrete and shows how a single website can be reachable over both.
IPv4 (32-bit, dotted decimal):
203.0.113.10
IPv6 (128-bit, hexadecimal, zeros collapsed with ::):
2001:0db8:85a3:0000:0000:8a2e:0370:7334
-> 2001:db8:85a3::8a2e:370:7334
DNS records that map a name to each:
example.com. A 203.0.113.10 ; IPv4
example.com. AAAA 2001:db8:85a3::8a2e:370:7334 ; IPv6How the two coexist today #
Rather than a hard switchover, the internet runs both protocols in parallel through an approach called dual-stack, where devices, networks, and servers speak IPv4 and IPv6 simultaneously and use whichever the other end supports. When your browser connects to a website, it typically tries both and picks the one that works, often preferring IPv6 where available. This is why the transition has been invisible to most people: your phone may reach a site over IPv6 on mobile data and IPv4 on some office network without you noticing. For website owners, dual-stack means a site should ideally be reachable over both, so no visitor is left out. In DNS terms that means publishing both an A record for IPv4 and an AAAA record for IPv6. Where an IPv6-only client must reach an IPv4-only server, translation technologies bridge the gap, though they add complexity. Our /services/vps-cloud-setup and /services/managed-hosting builds configure dual-stack where the host supports it, so a site serves visitors on either protocol seamlessly.
Does IPv6 affect website speed or SEO #
A common question is whether adopting IPv6 makes a website faster or ranks it higher, and the honest answer is: not directly, but it does not hurt and occasionally helps. IPv6 can slightly reduce latency in situations where it avoids the NAT translation that IPv4 requires, and some mobile networks are IPv6-first, so a site reachable over IPv6 may connect a touch faster for those users. However, page speed is dominated by far larger factors, image weight, caching, code efficiency, and server response time, so IPv6 is not a meaningful performance lever on its own; our /services/speed-optimization work focuses on those bigger wins first. On SEO, search engines crawl and index sites over both protocols and do not reward IPv6 with ranking boosts. The real value of IPv6 support is reach and future-proofing: as more networks become IPv6-native, being reachable over it ensures no segment of visitors is inconvenienced. Treat IPv6 as good hygiene and future readiness rather than a speed or ranking trick.
Security and practical considerations #
IPv6 changes a few security assumptions worth knowing. Because IPv6 restores unique public addresses to individual devices, the accidental firewall effect that NAT provided in IPv4, hiding internal devices behind one address, disappears, so IPv6 networks must rely on properly configured firewalls rather than address translation for that protection. This is a management difference, not a weakness; a well-configured IPv6 network is as secure as IPv4, but it must be configured deliberately. The larger address space also makes brute-force network scanning far harder, a mild security benefit. For website owners, the practical points are simpler: ensure your firewall rules cover both protocols so you do not accidentally leave IPv6 open while locking down IPv4, and confirm that security tools, logging, and access controls handle IPv6 addresses correctly. Our /services/website-security reviews check that both protocols are governed by consistent rules, since an oversight on one stack can quietly undermine hardening on the other. The goal is parity: whatever you protect on IPv4 should be equally protected on IPv6.
Private addresses, NAT, and your home network #
A detail that clears up much confusion is the difference between public and private IP addresses. Certain IPv4 ranges, such as 192.168.x.x and 10.x.x.x, are reserved for private networks and are not routable on the public internet; your home router assigns these to your devices, then uses NAT to share one public address for all of them. This is why every device on your network might show a 192.168.1.x address internally while the outside world sees a single public address. It is also why checking your IP on a website shows a different number than your computer's network settings report. IPv6, with its vast supply, reduces the need for this translation by giving devices unique addresses directly, though private addressing concepts still exist within it. For website owners, the practical relevance is that server access rules, firewall settings, and analytics may involve both public and private addresses, and our /services/managed-hosting team accounts for this distinction when configuring access. Knowing public versus private explains why the same device can appear to have two different addresses at once.
What this means for your website #
For most business owners, IPv4 versus IPv6 is something your host and DNS handle behind the scenes, and you rarely need to act. The sensible baseline is dual-stack: your site is reachable over both, meaning it works for every visitor regardless of their network, and you are ready as IPv6 adoption keeps growing. In practice this means your host supports IPv6 and your DNS publishes both A and AAAA records, which our /services/domains-dns-email and /services/managed-hosting teams set up where available. You do not need to abandon IPv4, it will remain in service for years, nor rush into IPv6-only, which would strand visitors on IPv4-only networks. If your current host does not support IPv6 at all, that is a minor future-proofing gap rather than an emergency, but it is worth noting when choosing infrastructure. If you are unsure how your site is configured or whether IPv6 visitors can reach it, a /free-website-audit will check both protocols and flag any addressing or DNS issue that could quietly exclude part of your audience.
FAQ
Why do we need IPv6 if IPv4 still works?
IPv4 works but ran out of addresses; its roughly 4.3 billion slots cannot cover the world's billions of connected devices. IPv6 provides an effectively unlimited supply, removing the scarcity that forces workarounds like NAT. IPv4 survives through those workarounds, but IPv6 is the long-term solution, which is why both run together during the ongoing transition.
Do I need IPv6 for my website?
You do not strictly need it, since most sites remain reachable over IPv4, but supporting both via dual-stack is best practice. It ensures visitors on IPv6-only or IPv6-first networks, including many mobile users, reach you smoothly, and it future-proofs your site. If your host offers IPv6, enabling it with an AAAA record is a low-effort improvement.
Is IPv6 faster than IPv4?
Only slightly, and only in specific cases where it avoids NAT translation or serves IPv6-first mobile networks. IPv6 is not a meaningful speed upgrade on its own; page performance depends far more on image size, caching, code, and server response. Adopt IPv6 for reach and future-readiness, not as a way to make your site noticeably faster.
What is the difference between an A record and an AAAA record?
Both are DNS records that point a domain at a server's IP address. An A record maps the domain to an IPv4 address like 203.0.113.10, while an AAAA record maps it to an IPv6 address like 2001:db8::1. A dual-stack site publishes both so visitors on either protocol can reach it.
Can IPv4 and IPv6 talk to each other directly?
No, not directly; the two are not backward compatible. An IPv6-only device cannot connect straight to an IPv4-only server without a translation mechanism in between. This incompatibility is why the internet runs dual-stack, with most devices and networks speaking both protocols at once so communication succeeds regardless of which format each end prefers.
Is IPv6 less secure than IPv4?
No, but it must be secured deliberately. IPv6 gives devices unique public addresses, so the incidental hiding that NAT provided under IPv4 is gone; protection relies on properly configured firewalls instead. A well-configured IPv6 network is as safe as IPv4. The key is applying consistent firewall and access rules to both protocols, leaving neither exposed.
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