Networking · 9 min read · May 12, 2026 · IPLocatorTools

IPv4 vs IPv6 Explained: What's the Difference and Why It Matters

IPv4 addresses are running out. IPv6 is the solution. Here's what the difference actually means for you, your network, and the future of the internet.

If you have ever looked at your IP address and seen a long string of letters and numbers separated by colons, you have seen an IPv6 address. If you have seen four numbers separated by dots, that is IPv4. Most internet connections today actually have both — and understanding the difference matters more than most people realise.

You can check which version your current connection uses right now at IPLocatorTools. The tool displays both your IPv4 and IPv6 addresses if your connection supports both.

What is IPv4?

IPv4 stands for Internet Protocol version 4. It was defined in 1981 and has been the foundation of internet addressing ever since. An IPv4 address looks like this:

203.0.113.42

Four numbers separated by dots, each ranging from 0 to 255. Technically, each number is an 8-bit value (called an octet), so an IPv4 address is 32 bits in total.

A 32-bit address space allows for 2³² unique addresses — approximately 4.29 billion. In 1981, with a few hundred computers on the internet, this seemed impossibly large. By 2011, the Internet Assigned Numbers Authority (IANA) had allocated the last remaining IPv4 address blocks to regional registries. The world has effectively run out of new IPv4 addresses.

What is IPv6?

IPv6 stands for Internet Protocol version 6. It was developed through the 1990s specifically to replace IPv4 and solve the address exhaustion problem. An IPv6 address looks like this:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Eight groups of four hexadecimal digits, separated by colons. Each group is 16 bits, making an IPv6 address 128 bits in total.

A 128-bit address space allows for 2¹²⁸ unique addresses — approximately 340 undecillion (that is 340 followed by 36 zeros). To put this in perspective: there are enough IPv6 addresses to assign billions of addresses to every grain of sand on Earth. IPv6 exhaustion is not a concern for the foreseeable future.

IPv4 vs IPv6 — Side by Side

| Feature | IPv4 | IPv6 | |---------|------|------| | Address length | 32 bits | 128 bits | | Address format | 203.0.113.42 | 2001:db8::8a2e:370:7334 | | Total addresses | ~4.3 billion | ~340 undecillion | | Header size | 20 bytes minimum | 40 bytes fixed | | NAT required | Often needed | Not needed | | Built-in security | No (IPSec optional) | IPSec built in | | Auto-configuration | Requires DHCP | Supports SLAAC | | Broadcast | Yes | No (uses multicast) | | Deployment | Universal | Growing rapidly |

IPv6 Address Notation — The Rules

IPv6 addresses can be abbreviated to make them more readable. There are two rules:

Rule 1 — Leading zeros in each group can be removed: 2001:0db8:0000:0000 becomes 2001:db8:0:0

Rule 2 — One consecutive sequence of all-zero groups can be replaced with ::: 2001:db8:0:0:0:0:0:1 becomes 2001:db8::1

The :: can only appear once in an address. If you see ::1, that is the IPv6 loopback address (equivalent to 127.0.0.1 in IPv4 — it refers to the local device itself).

Common special IPv6 addresses:

• ::1 — Loopback (localhost)
• :: — Unspecified address (all zeros)
• fe80::/10 — Link-local addresses (auto-assigned, not routable)
• 2001:db8::/32 — Documentation range (not used in real networks)
• fc00::/7 — Unique local addresses (private, like 192.168.x.x in IPv4)

Why Did We Run Out of IPv4 Addresses?

The designers of IPv4 in 1981 allocated certain ranges as private (not routable on the public internet) and reserved others for special purposes, which reduced the effective public address space. The explosion of internet-connected devices — smartphones, tablets, smart home devices, IoT sensors, cloud servers, containers — consumed the remaining public IPv4 addresses far faster than anyone anticipated.

Several mechanisms were developed to extend IPv4's life:

NAT (Network Address Translation) — A router translates between a single public IP address and many private IP addresses on the local network. Your home has one public IP shared by all your devices. This dramatically reduced IPv4 demand but also created complexity and broke some peer-to-peer applications.

Carrier-Grade NAT (CGNAT) — ISPs run NAT at their network level, sharing a single public IPv4 address among multiple customers. This further conserved IPv4 addresses but causes problems for applications that need direct incoming connections.

IPv4 address markets — Since IANA stopped allocating new IPv4 addresses, a secondary market developed where companies sell their unused IPv4 allocations. A single IPv4 address trades for around $40–60 USD. Some organisations with large legacy allocations (universities, corporations that received big blocks in the early internet era) have sold portions of their unused ranges.

What is Dual-Stack?

Dual-stack means a device or network supports both IPv4 and IPv6 simultaneously. This is the current standard for most modern internet infrastructure.

When your device connects to a dual-stack server, modern operating systems use a mechanism called Happy Eyeballs (RFC 8305) to determine which protocol to use. The device tries both IPv6 and IPv4 connections simultaneously and uses whichever responds first — with a slight preference for IPv6. In practice, most connections to dual-stack servers use IPv6 automatically.

If you visit IPLocatorTools and see both an IPv4 and IPv6 address displayed, your connection is dual-stack. If you only see an IPv4 address, your ISP or router does not yet support IPv6.

IPv6 Advantages Beyond Just Address Space

IPv6 was not designed only to solve address exhaustion. It introduced several technical improvements:

Simplified Header

The IPv4 packet header has many optional fields that make processing complicated. IPv6 has a fixed 40-byte header with a cleaner, more efficient structure. This makes routing faster and more predictable, especially at the router level where millions of packets are processed per second.

Stateless Address Autoconfiguration (SLAAC)

IPv6 devices can automatically configure their own IP addresses without a DHCP server. A device generates a link-local address (starting with fe80::) from its network interface hardware address and uses it to discover the network prefix from the router. This simplifies network configuration in large deployments.

No Broadcast

IPv4 uses broadcast to send messages to all devices on a network segment. IPv6 replaces broadcast with multicast, where messages are sent only to the specific group of devices that need to receive them. This reduces unnecessary network traffic.

IPSec Built In

IPv6 was designed with IPSec (IP Security) as a core component rather than an optional add-on. While IPv6 IPSec is not always enforced, its standardised presence makes end-to-end encryption more straightforward to implement.

No NAT Required

Because every device can have its own globally unique IPv6 address, there is no need for NAT. This restores the original end-to-end connectivity model of the internet, where any device can directly communicate with any other device. This simplifies peer-to-peer applications, gaming, video calls, and IoT device connectivity.

IPv6 Adoption — Where Are We in 2026?

IPv6 adoption has grown steadily but unevenly:

• Google reports approximately 45–50% of its users connect over IPv6
• Major ISPs in the US, Germany, India, and Japan have high IPv6 deployment rates
• Mobile networks have strong IPv6 support — mobile carriers in many countries have deployed IPv6 extensively because CGNAT is particularly problematic for mobile traffic patterns
• Cloud providers (AWS, Google Cloud, Azure, Cloudflare) fully support IPv6 on all services
• Some regions — particularly parts of Southeast Asia, Eastern Europe, and smaller ISPs — still have limited IPv6 deployment

The transition is gradual because the internet infrastructure is enormous and IPv6 requires updates across routers, ISPs, servers, applications, and devices. IPv4 will not disappear overnight — dual-stack operation will continue for many years.

Does IPv6 Affect Your Privacy?

Yes, and this is an important consideration.

IPv4 privacy: With CGNAT, multiple users share a single public IPv4 address, making it harder to correlate an IP with a specific user. Dynamic IPv4 addresses also change periodically.

IPv6 privacy concern: Early IPv6 implementations used the device's hardware MAC address to generate the last 64 bits of the IPv6 address (this is called EUI-64 format). This created a globally unique, persistent identifier embedded in your IP address that could track your device across networks and across time — a significant privacy regression.

IPv6 Privacy Extensions (RFC 4941) solved this. Privacy extensions generate random temporary IPv6 addresses that change periodically (typically every few hours to days). Modern operating systems (Windows, macOS, iOS, Android, Linux) enable privacy extensions by default, so your IPv6 address should not be derived from your hardware address.

You can verify this: if your IPv6 address contains the pattern ff:fe in the middle of the interface identifier portion (the last 64 bits), it was derived from a MAC address and privacy extensions are not working. Most modern systems will show a randomised address instead.

How to Check Your IPv6 Address

Visit IPLocatorTools and your IPv6 address is displayed automatically if your connection supports it. If you only see an IPv4 address, your ISP or home router does not yet support IPv6.

To check on Windows: Open Command Prompt and type ipconfig. Look for "IPv6 Address" under your active network adapter. Addresses starting with fe80:: are link-local (internal network only). A globally routable IPv6 address starts with 2 or 3.

To check on Mac: Open Terminal and type ifconfig | grep inet6. Addresses starting with fe80 are link-local. Globally routable addresses start with 2 or 3.

To check if a website supports IPv6: Use the DNS Lookup tool, enter the domain, and select AAAA record type. If an AAAA record exists, the site has an IPv6 address and can be reached over IPv6.

Why Some Websites Still Only Have IPv4

IPv6 adoption requires work on the server side too. Website operators must:

1. Obtain an IPv6 address block from their hosting provider
2. Configure their web server to listen on the IPv6 address
3. Add an AAAA record in DNS pointing to the IPv6 address
4. Ensure their firewall allows IPv6 traffic

Many smaller websites, legacy applications, and older hosting setups still only support IPv4. Until they add AAAA records, your device will fall back to IPv4 to connect to them, even if your connection supports IPv6.

Frequently Asked Questions

Will IPv6 replace IPv4 completely? Eventually, but not soon. The internet will run both simultaneously for many years. The transition to full IPv6-only will likely take another decade or more.

Is IPv6 faster than IPv4? In theory, IPv6 has a slight efficiency advantage due to its cleaner header and no NAT overhead. In practice, the speed difference is negligible for end users. What matters more is the quality of your ISP's network and the geographic distance to servers.

Do I need to do anything to use IPv6? No, if your ISP and router support it, your devices will use IPv6 automatically. You do not need to configure anything manually. If you want to enable IPv6 on a network that supports it but where your router does not have it enabled, check your router's settings for an IPv6 or "Internet Protocol version 6" option.

Can IPv6 addresses be geolocated? Yes. IPv6 address blocks are allocated by the same regional internet registries (ARIN, RIPE, APNIC, etc.) as IPv4, and geolocation databases cover IPv6 ranges. The accuracy is similar to IPv4 geolocation — highly accurate at country level, approximately accurate at city level.

What is an IPv6-only network? An IPv6-only network uses only IPv6 addresses with no IPv4 support. Some mobile carriers operate IPv6-only networks for new subscribers, using a technology called NAT64/DNS64 to translate connections to IPv4-only servers. This is transparent to most users and applications.

Related Tools

Check your current IPv4 and IPv6 addresses at IPLocatorTools. Use the DNS Lookup tool to check if any domain has an AAAA record (IPv6 support). Use Domain Tools for WHOIS and reverse DNS lookups on both IPv4 and IPv6 addresses.