IPv4 vs IPv6: What's the Difference?

The Story Behind IPv4

IPv4 was standardized in 1981 and uses 32-bit addresses, providing approximately 4.3 billion unique addresses. When the internet was young, this seemed like more than enough. Each address is written as four numbers between 0 and 255, separated by dots — for example, 74.125.224.72. For decades, IPv4 worked well. But as the number of internet-connected devices exploded — smartphones, tablets, IoT devices, smart home gadgets, servers — the pool of available IPv4 addresses started running out. By the early 2010s, Regional Internet Registries were reporting exhaustion of their IPv4 address pools.

Enter IPv6

IPv6 was developed in the late 1990s specifically to address the IPv4 shortage. It uses 128-bit addresses, providing approximately 3.4 × 10³⁸ unique addresses. An IPv6 address looks quite different from IPv4: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. The massive address space of IPv6 means we can assign a unique address to every device on the planet — and still have room to spare. This eliminates the need for the workarounds that have extended IPv4's life, such as NAT.

Key Differences

Address format: IPv4 uses dotted decimal notation (192.168.1.1), while IPv6 uses hexadecimal with colons (2001:db8::1). Address space: IPv4 offers ~4.3 billion addresses; IPv6 offers ~3.4 × 10³⁸. Configuration: IPv6 supports auto-configuration (SLAAC), allowing devices to assign themselves addresses. IPv4 typically requires DHCP or manual configuration. Security: IPv6 was designed with IPsec (Internet Protocol Security) support built in, though its use is optional. IPv4 can also use IPsec but it's not native to the protocol. Performance: IPv6 has a simplified header structure that can improve routing efficiency. It also eliminates the need for NAT, which can reduce latency for peer-to-peer connections. Fragmentation: In IPv4, routers can fragment packets. In IPv6, only the sender can fragment packets, which simplifies router processing.

The Transition Today

The transition from IPv4 to IPv6 is ongoing and gradual. Most modern operating systems, routers, and internet service providers support both protocols simultaneously (dual-stack). Many major websites and services are already accessible via IPv6. For everyday users, the transition is largely transparent. Your devices and network likely already support IPv6 without you needing to do anything. You can check whether you have IPv6 connectivity using tools like our IP Tester homepage.