IPv4 vs IPv6 — What's the Difference?
IPv4 and IPv6 are two versions of the Internet Protocol. IPv4 has been the backbone of the internet since 1983, but its limited address space led to the development of IPv6.
Quick Comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Format | 192.168.1.1 | 2001:db8::1 |
| Total addresses | ~4.3 billion | ~340 undecillion |
| NAT required? | Often yes | No — end-to-end |
| Header | Variable length | Fixed 40 bytes |
| IPsec | Optional | Built-in |
The Address Exhaustion Problem
IPv4's 4.3 billion addresses seemed infinite in 1983. IANA allocated the last IPv4 blocks in 2011. Today, we rely on NAT (Network Address Translation) to share public IPs among multiple devices — a workaround, not a solution.
IPv6 Adoption
As of 2025, Google reports about 45% of users access their services over IPv6. Adoption varies by country — India, the US, and Germany lead. Many ISPs now assign both IPv4 and IPv6 addresses (dual-stack).
Try It
Use our IP Lookup tool to check whether an address is IPv4 or IPv6.