IPv4 uses 32-bit addresses and supports roughly 4.3 billion unique IPs. IPv6 uses 128-bit addresses and supports 340 undecillion — a number so large it loses physical meaning. The internet is running on both at once, but for very different reasons, and the practical differences matter when you debug a connection or design a service.
The headline differences
| IPv4 | IPv6 | |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Total address space | ~4.3 × 10⁹ | ~3.4 × 10³⁸ |
| Notation | 93.184.216.34 |
2606:2800:220::1946 |
| Notation base | Decimal, dotted | Hexadecimal, colon-separated |
| Header size | 20 bytes (variable) | 40 bytes (fixed) |
| Address configuration | DHCP or manual | SLAAC, DHCPv6, or manual |
| NAT required at scale | Yes (CGNAT, home NAT) | No (true end-to-end) |
| Built-in IPsec | Optional | Mandatory in spec (but rarely deployed end-to-end) |
Why IPv6 exists at all
The math is simple: 32 bits gives you 4,294,967,296 unique addresses, which sounded infinite in 1981 but is now smaller than the global population of internet-connected devices. The Internet Assigned Numbers Authority handed out the last block of unallocated IPv4 space in 2011. Since then, ISPs have stretched IPv4 with carrier-grade NAT (CGNAT), where dozens of subscribers share one public IP. CGNAT works for browsing but breaks peer-to-peer apps, gaming servers, and anything that needs an inbound connection.
IPv6 solves the problem at the source by giving the entire IPv6 address space to every network operator with room to spare. A typical home gets a /56 or /60 block — that is roughly 4.7 sextillion addresses for one household, which is more than every IPv4 address in existence, multiplied by itself.
What changes in practice
For most users, nothing. Modern operating systems prefer IPv6 when both are available and fall back to IPv4 transparently. For operators and engineers, the changes are real:
- No NAT means peer-to-peer comes back. Direct connections work again — useful for gaming, VoIP, WebRTC, and IoT.
- Privacy extensions matter. A device's IPv6 address can be derived from its MAC, which is a tracking vector. Operating systems now generate privacy addresses (RFC 4941) that rotate periodically.
- Firewalling changes. With every device globally addressable, firewall rules must be explicit; you cannot rely on NAT to hide internal services by accident.
- Logs get longer. Plan for 39-character addresses in databases, logs, and analytics.
How adoption looks in 2026
Global IPv6 adoption hovers around 45–50% in early 2026 measured by Google's traffic, with wide variance by country and carrier. India, the United States, France, and Germany are above 60%, driven by mobile networks rolling out IPv6 by default. Some regions and ISPs are still under 5%. Big-tech CDNs (Cloudflare, Fastly, Akamai, Google) serve everything dual-stack. The headline: you cannot run a serious internet service without supporting IPv6 anymore.
Which one do you have right now?
Open IPeek — if your connection supports both, you will see your IPv4 and IPv6 addresses side-by-side, with the network operator each is announced from. If you only see an IPv4, your ISP either has not rolled out IPv6 or you are on a network (typically a corporate VPN or older router) that strips it.
The takeaway
IPv4 and IPv6 are not rivals — they are layered. IPv4 is the legacy protocol holding the internet together through NAT and clever address reuse; IPv6 is the long-term replacement that restores the original peer-to-peer promise. The interesting question for the next five years is not if IPv6 takes over — it is which infrastructure (CGNAT, NAT64, dual-stack) gets retired first.