Quick summary: IPv4 uses 32‑bit addresses and is running out of space; IPv6 uses 128‑bit addresses, offers built‑in security and autoconfiguration, and is the future of the internet. Below we compare them feature‑by‑feature and show you how to get your network ready.
1. Address Space
IPv4 supports ~4.3 billion unique addresses—insufficient for 15 billion IoT devices plus phones, laptops and servers. IPv6 expands the pool to 340 undecillion (that’s 3.4×1038). In practice, that means every grain of sand on Earth could have its own subnet.
2. Notation & Human Readability
- IPv4: dotted decimal, e.g.
203.0.113.42 - IPv6: hexadecimal, e.g.
2001:db8:85a3::8a2e:370:7334
IPv6 addresses can be compressed by omitting leading zeros and collapsing consecutive zero groups with
::.
3. Header Differences
IPv6’s header is streamlined to a fixed 40 bytes, improving router efficiency. Optional features move to extension headers, making basic forwarding faster.
4. Security Features
IPsec is optional in IPv4 but mandatory in IPv6. While most consumer routers don’t enforce it by default, enterprises can require encrypted IPv6 end‑to‑end tunnels without extra protocols.
5. NAT vs End‑to‑End Connectivity
NAT (Network Address Translation) lets multiple devices share one IPv4 public address but breaks end‑to‑end principles. IPv6’s abundance eliminates the need for NAT, simplifying peer‑to‑peer apps and VoIP.
6. Adoption Statistics
As of 2025, Google’s public stats show global IPv6 usage at ~46 %. The U.S. leads at 55 %, India at 66 %, while some regions (e.g., parts of Africa) still sit below 5 %. Dual‑stack deployments dominate: ISPs hand out both protocols while legacy hardware phases out.
7. Migration Strategies
Dual‑Stack
Run IPv4 and IPv6 in parallel; preferred for gradual transitions.
Tunneling
Encapsulate IPv6 inside IPv4 (6in4, Teredo) or vice‑versa (464XLAT) when carriers can’t offer native service.
Translation Gateways
NAT64/DNS64 lets IPv6‑only clients reach IPv4‑only servers.
8. Developer Impact
- Use
AF_INET6socket families and prefer domain names over hard‑coded literals. - Store client IPs in 128‑bit fields (or text) in databases.
- Whitelist firewalls for both protocols; IPv6 often bypasses poorly configured rules.
9. Is IPv6 Faster?
Usually yes, because traffic bypasses CGNAT and routers process simpler headers. Real‑world benchmarks show 5‑15 % latency improvement on dual‑stack mobile networks.
10. How to Check Which Version You’re Using
Visit the Get My IP home page. If you see colons (:) in your address, it’s
IPv6; if it’s dots (.), IPv4. Your browser prefers IPv6 when available.
Key Takeaways
- IPv6 solves address exhaustion and removes NAT complexity.
- Security (IPsec), autoconfig (SLAAC) and routing efficiency are built‑in.
- Adoption is accelerating; make your code and network dual‑stack today.