IPv4 vs IPv6: What's the Difference and Why It Matters
The internet is running out of IPv4 addresses. IPv6 has been the “solution” for 25 years. Here's why we're still stuck in between.
Key Takeaway
IPv4 addresses ran out years ago. IPv6 has 340 undecillion addresses. But NAT made IPv4 “good enough,” so adoption has been painfully slow. In 2026, about 45% of internet traffic uses IPv6. You probably have both and never noticed.
Unallocated IPv4 Addresses Remaining
~4,294,967,296
IANA distributed the last IPv4 blocks in February 2011. Regional registries have since exhausted their pools. New IPv4 addresses come from trading existing allocations at $30-50 per address.
Side-by-Side Comparison
Everything you need to know in one table. The differences go far beyond just address length.
What They Actually Look Like
IPv4 Address
192.168.1.1
4 groups of decimal numbers separated by dots. Each group ranges from 0 to 255. Total: 32 bits.
IPv6 Address
2001:0db8:85a3:0000:0000:8a2e:0370:7334
8 groups of 4 hex digits separated by colons. Leading zeros can be omitted, consecutive zero groups collapsed with “::”. Total: 128 bits.
That IPv6 address above can be shortened to 2001:db8:85a3::8a2e:370:7334 — same address, compressed notation. The “::” replaces one or more groups of all zeros.
Check Your Connection
See which protocol your connection is using right now. Most modern connections support both (dual-stack).
We'll check for both IPv4 and IPv6 connectivity.
How We Ran Out of 4.3 Billion Addresses
When IPv4 was designed in 1981, 4.3 billion addresses felt infinite. The internet was a research project connecting a few hundred universities. Nobody anticipated that in 2026, a single household might have 20 connected devices — phones, laptops, TVs, thermostats, cameras, light bulbs, refrigerators.
The first major waste was “classful” allocation. In the early days, organizations were given entire Class A blocks of 16.7 million addresses. MIT, IBM, Ford, and the US Department of Defense each received blocks that large. Most of those addresses went unused. Some organizations still hold these blocks today.
IANA (the Internet Assigned Numbers Authority) gave out the last blocks of IPv4 addresses to regional registries in February 2011. APNIC (Asia-Pacific) exhausted their pool first, in April 2011. RIPE (Europe) followed in 2012, LACNIC (Latin America) in 2014, and ARIN (North America) in 2015. AFRINIC (Africa) ran out in 2020.
Today, new IPv4 addresses are available only through a secondary market. Organizations buy and sell existing allocations, with prices ranging from $30-50 per address. Amazon spent over $100 million acquiring IPv4 address blocks. This market exists because the transition to IPv6 has been far slower than anyone predicted.
Why IPv6 Adoption Is Painfully Slow
IPv6 was standardized in 1998. Twenty-eight years later, global adoption sits around 45%. To understand why, you need to understand NAT — the technology that kept IPv4 alive way past its expiration date.
NAT (Network Address Translation) lets hundreds of devices share a single public IPv4 address. Your home router does this: your laptop, phone, and smart TV all use private addresses (192.168.x.x) and your router translates them to a single public IP. This clever hack reduced the urgency to adopt IPv6, because IPv4 suddenly “had enough” addresses again.
But NAT is also why certain things are harder than they should be. Hosting a game server, setting up a home security camera for remote access, or making peer-to-peer calls all require port forwarding because NAT breaks the end-to-end connectivity model. IPv6 would eliminate all of these problems because every device gets a globally unique address.
NAT works well enough
ISPs invested billions in NAT infrastructure. It solves the immediate address shortage. The business case for IPv6 migration is weak when NAT already works.
Upgrade costs are massive
Every router, firewall, load balancer, and network monitoring tool needs to support IPv6. For a major ISP with millions of devices, this is a multi-year, multi-million dollar project.
No direct compatibility
IPv4 and IPv6 are completely separate protocols. You cannot send an IPv4 packet to an IPv6 address or vice versa. This means running both simultaneously (dual-stack) during the transition, doubling operational complexity.
Staff need retraining
Network engineers who have spent their careers working with IPv4 need to learn new addressing schemes, new security models, and new troubleshooting tools. The hex notation alone trips people up.
How the Transition Actually Works
Since IPv4 and IPv6 are not compatible, the internet uses three strategies to bridge them during the transition. Understanding these helps explain why the whole process is so slow.
Dual-Stack
Run both IPv4 and IPv6 simultaneously on every device and network link. The most common approach today. Clean but expensive — you maintain two complete network stacks.
Tunneling
Wrap IPv6 packets inside IPv4 packets to send them across IPv4-only networks. Technologies like 6in4, 6to4, and Teredo. Works but adds latency and complexity.
NAT64/DNS64
Translate between IPv6 and IPv4 at a gateway. Lets IPv6-only clients access IPv4 servers. Used by mobile carriers (T-Mobile US, for example) to run IPv6-only networks.
Security: IPv6 Was Designed with It In Mind
IPv4 was built in an era when the internet was a trusted research network. Security was an afterthought, bolted on later through optional extensions like IPsec. IPv6 was designed with mandatory IPsec support, meaning every IPv6 implementation must support encryption and authentication at the network layer.
In practice, this does not mean all IPv6 traffic is encrypted. IPsec is mandatory to support, not mandatory to use. Most IPv6 traffic today is unencrypted, just like IPv4. The encryption happens at higher layers (HTTPS/TLS) regardless of the IP version.
One genuine security concern with IPv6: the larger address space makes network scanning impractical (good for defenders), but IPv6 Privacy Extensions that rotate addresses can make tracking users harder (good for privacy, harder for abuse prevention). NAT in IPv4 accidentally provided a layer of obscurity that IPv6 removes by giving every device a public address.
What This Means For You (Honestly)
If you are a regular internet user, IPv4 vs IPv6 does not affect your daily life much. Your devices handle both transparently. You will never need to manually type an IPv6 address. Your ISP either supports IPv6 or it does not, and you probably have no choice in the matter.
If you run a website or online service, you should support IPv6. Google, Facebook, Netflix, and every major CDN have been IPv6-enabled for years. If your hosting does not support IPv6, a growing percentage of users are reaching your site through translation layers, which adds latency.
If you work in networking, IPv6 is a career skill worth investing in. The transition is slow, but it is happening. Major mobile carriers are already IPv6-primary. Cloud providers default to dual-stack. Understanding both protocols — and the transition mechanisms between them — is increasingly expected for network engineering roles.
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Frequently Asked Questions
In theory, yes. IPv6 eliminates NAT translation, removing a processing step. In practice, the speed difference is negligible for most users — typically 1-5ms less latency. The real advantage is for IoT devices and peer-to-peer connections where NAT traversal adds significant overhead.
For now, yes. Most of the internet still runs on IPv4, so you need IPv4 connectivity to reach all websites. IPv6 is a bonus that provides better routing to sites that support it. Most modern ISPs run dual-stack networks that give you both automatically.
No. IPv4 will continue working for many years. The internet cannot simply turn off IPv4 because too much infrastructure depends on it. The transition to IPv6 is gradual — both protocols will coexist for at least the next decade.
Visit our My IP page (whatismylocation.org/my-ip) which shows both your IPv4 and IPv6 addresses. You can also use our IPv6 Tools page for a complete connectivity test.
Three main reasons: NAT made IPv4 exhaustion manageable, upgrading network equipment is expensive and risky for ISPs, and IPv4/IPv6 are not directly compatible — requiring dual-stack infrastructure during transition. As of 2026, global adoption is around 45%.
Yes, and in some ways more easily. IPv6 addresses were originally designed to include the device's MAC address. Modern systems use Privacy Extensions that rotate addresses. Your ISP still assigns your IPv6 prefix, which is traceable to your account just like IPv4.
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