IPv4 was standardised in 1981, when a few hundred machines were connected and 4.3 billion addresses looked like an absurd surplus. IPv6 was designed in the late 1990s by people who could already see the wall coming. The regional registries began running out of fresh IPv4 blocks in 2011, and the last of them exhausted their free pools within the decade.
Side by side
| IPv4 | IPv6 | |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Total addresses | About 4.3 billion | About 340 undecillion |
| Notation | Decimal, dot-separated | Hexadecimal, colon-separated |
| Example | 203.0.113.42 | 2001:db8::8a2e:370:7334 |
| Configuration | DHCP or manual | Autoconfiguration built in |
| NAT | Essential in practice | Unnecessary |
| IPsec encryption | Optional add-on | Part of the original design |
| Broadcast | Yes | Replaced by multicast |
| Header | Variable length, 20+ bytes | Fixed 40 bytes, simpler to route |
How big is the IPv6 space, really?
The number 340 undecillion means nothing to anyone, so here is a way to hold it. IPv4 offers fewer addresses than there are people alive. IPv6 offers roughly 1028 addresses for every person on Earth. Even allocating enormous blocks wastefully — and IPv6 policy deliberately does allocate generously, because address scarcity was the whole problem — exhaustion is not a scenario anyone plans for.
Your home connection, on an IPv6 provider, is typically handed a /56 or /64 prefix. A single /64 contains more addresses than the entire IPv4 internet, squared.
Reading an IPv6 address
Eight groups of four hexadecimal digits, separated by colons. Two shortcuts make them shorter than
they look. Leading zeros in a group are dropped, so 0db8 becomes db8. And
one run of consecutive all-zero groups collapses to ::, which may appear only once per
address so the expansion stays unambiguous.
So 2001:0db8:0000:0000:0000:0000:0000:0001 is normally written
2001:db8::1. Both are the same address.
The NAT question
IPv4 survived past exhaustion because of Network Address Translation, which lets a whole household share one public address. That was a brilliant stopgap with real costs: it broke the assumption that any host can reach any other host directly, which is why peer-to-peer applications, game hosting and VoIP all need workarounds like STUN, UPnP and manual port forwarding.
IPv6 gives every device its own globally unique address, so those workarounds become unnecessary. People sometimes read that as "IPv6 removes my firewall", which is wrong. Addressability is not reachability: your router still firewalls unsolicited inbound traffic by default. What changes is that when you do want a direct connection, it simply works.
Is IPv6 faster?
Sometimes, modestly, and not for the reason people assume. The IPv6 header is fixed-length and simpler, so routers do slightly less work per packet, and skipping NAT removes a translation step. In practice the measurable gains come from the fact that IPv6 traffic often takes newer, better provisioned network paths, particularly on mobile networks.
Do not expect a visible difference on a normal home connection. The improvement is real but small compared to your line speed and your Wi-Fi.
Is IPv6 more secure?
Marginally, with an asterisk. IPsec was mandatory in the original IPv6 specification and is optional in IPv4, but in practice most traffic is protected by TLS at a higher layer regardless of version, so the practical difference is smaller than it sounds.
There is a genuine privacy consideration. Early IPv6 autoconfiguration derived the address from the device's hardware MAC address, which made a device trackable across networks. Privacy extensions, which rotate the host portion of the address, are now on by default in every mainstream operating system and solve this.
Why the transition took so long
The two protocols are not interoperable. An IPv6-only host cannot talk to an IPv4-only server, which creates a coordination problem: no network operator gains much by moving first, and no content provider wants to be unreachable to the majority.
The answer was dual stack. Nearly every modern connection runs both simultaneously, preferring IPv6 when both ends support it and falling back silently to IPv4 otherwise. Your device does this on every single connection, and you never notice. It is also why the homepage may show you an IPv6 address as your primary one while still listing an IPv4 address underneath.
What you should actually do
Nothing, in almost every case. IPv6 support is handled by your operating system and your router. If you are curious whether your connection has it, the homepage tells you directly — if the IPv6 field shows an address, you are already dual-stacked.
If you run infrastructure, the calculus is different: publish AAAA records, test your services over IPv6, and stop assuming every client address fits in 32 bits. Our subnet calculator covers the IPv4 arithmetic you still need day to day.