IPv4 vs IPv6
Side-by-side comparison of the two Internet Protocol versions — how they differ in addressing, routing, security, and real-world adoption.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32-bit (4 bytes) | 128-bit (16 bytes) |
| Total addresses | 4.29 billion (2³²) | 340 undecillion (2¹²⁸) |
| Format | 192.0.2.42 (dotted decimal) |
2001:db8::8a2e:370:7334 (colon hex) |
| Header size | 20–60 bytes (variable) | 40 bytes (fixed) |
| Fragmentation | Routers and sender | Sender only (Path MTU Discovery) |
| NAT required? | Yes — common due to exhaustion | No — every device gets a global address |
| IPsec | Optional add-on | Built-in (mandatory support) |
| Broadcast | Yes (e.g. 255.255.255.255) | No — uses multicast instead |
| Checksum | Header checksum field | Removed (handled by lower layers) |
| Configuration | DHCP or manual | SLAAC (stateless auto-config) + DHCPv6 |
| DNS record | A record |
AAAA record |
| Reverse DNS zone | .in-addr.arpa |
.ip6.arpa |
| IANA exhaustion | Feb 2011 (top-level free pool) | Not expected for centuries |
| Adoption (2026) | ~55% of traffic | ~45% of Google users |
Why IPv4 is still dominant
Despite IPv6 being standardized in 1998, IPv4 still carries the majority of Internet traffic. The main reasons:
- NAT "solved" the problem — Network Address Translation lets millions of devices share one public IPv4 address. This reduced the urgency to migrate.
- Migration cost — dual-stack (running IPv4 + IPv6 simultaneously) is expensive. Equipment, training, and testing all take time and money.
- IPv4 address market — organizations can buy/sell IPv4 blocks on the secondary market ($30–$50 per address in 2026), extending IPv4's useful life.
- Content availability — most content is accessible over IPv4; only ~30% of the Alexa Top 1000 is reachable over IPv6-only.
IPv6 adoption leaders
Countries with the highest IPv6 adoption rates (percentage of traffic served over IPv6):
The transition timeline
- 1981 — IPv4 defined in RFC 791.
- 1998 — IPv6 standardized in RFC 2460.
- 2011 — IANA allocates the last IPv4 /8 blocks to APNIC. Top-level free pool exhausted.
- 2012 — World IPv6 Launch day (June 6). Major ISPs and content providers enable IPv6 permanently.
- 2014–2015 — LACNIC and ARIN free pools exhausted.
- 2019 — RIPE NCC runs out of IPv4 addresses.
- 2026 — ~45% of global traffic uses IPv6. Full transition remains years away.
Explore IPv4 data
WorldIP.io tracks every allocated IPv4 address, ASN, and organization. IPv6 support is on the roadmap.