IPv4 vs IPv6 - What's the Difference?
IPv4 and IPv6 are the two versions of the Internet Protocol in use today. IPv4, introduced in 1981, uses 32-bit addresses and is running out of space. IPv6, standardized in 1998, uses 128-bit addresses and provides a practically unlimited address pool. Both protocols coexist on most modern networks through a technique called dual-stack.
Side-by-Side Comparison
| Feature | IPv4 | IPv6 |
|---|
| Address length | 32 bits | 128 bits |
| Address format | Dotted decimal: 192.168.1.1 | Colon-hex: 2001:0db8:85a3::8a2e:0370:7334 |
| Total addresses | ~4.3 billion (2³²) | ~340 undecillion (2¹²⁸) |
| Address exhaustion | Exhausted globally since 2011 | No exhaustion concern |
| NAT required | Yes, for most home/business networks | No - Every device gets a public IP |
| Header size | 20–60 bytes (variable) | 40 bytes (fixed) |
| Checksums in header | Yes | No - Handled by transport layer |
| IPsec support | Optional | Mandatory (built-in) |
| Autoconfiguration | Requires DHCP | SLAAC - Devices configure themselves |
| Broadcast | Supported | Replaced by multicast |
| Global internet share (2025) | ~60–65% of traffic | ~35–40% of traffic |
IPv6 Address Types
| Type | Prefix | Purpose |
|---|
| Global Unicast | 2000::/3 | Globally routable - The equivalent of a public IPv4 address |
| Link-Local | fe80::/10 | Auto-assigned on every interface; not routed beyond the local link |
| Unique Local | fc00::/7 | Private addresses (similar to 192.168.x.x); not globally routable |
| Loopback | ::1/128 | Equivalent to 127.0.0.1 in IPv4 |
| Multicast | ff00::/8 | One-to-many delivery; replaces IPv4 broadcast |
| Anycast | From global unicast space | One IP assigned to multiple nodes; nearest responds |
Do You Need to Worry About IPv6?
- Most ISPs now assign IPv6 addresses alongside IPv4 (dual-stack). Your device likely has both already.
- IPv6 removes the need for NAT, so every device can be directly addressable - Firewalls become even more important.
- VPN users should check for IPv6 leaks: some VPNs only tunnel IPv4 traffic, exposing your real IPv6 address.
- Web performance can be better over IPv6 due to the simpler header and removal of NAT traversal overhead.
