Guide
IPv4 vs IPv6
Compare IPv4 and IPv6 addressing: format, address space, NAT, security, speed and how to check whether your connection already supports IPv6.
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Side-by-side comparison
| Property | IPv4 | IPv6 |
|---|---|---|
| Format | 203.0.113.45 | 2001:db8:85a3::8a2e:370:7334 |
| Length | 32 bits | 128 bits |
| Total addresses | ~4.3 billion | ~340 undecillion |
| Configuration | DHCP or manual | Stateless autoconfiguration (SLAAC) or DHCPv6 |
| NAT | Almost always required | Rarely needed — every device can be globally addressable |
| Header | Variable length, checksum | Fixed 40-byte header, no checksum — cheaper to route |
| Broadcast | Yes | Replaced by multicast and anycast |
| IPsec | Optional add-on | Designed in from the start |
Why IPv6 exists
IPv4's 4.3 billion addresses seemed limitless in 1981. The regional registries exhausted their free pools between 2011 and 2019, and IPv4 blocks now trade on a secondary market for tens of dollars per address. IPv6 solves the shortage permanently: a single residential allocation (a /64) contains more addresses than the entire IPv4 internet.
Is IPv6 faster?
Sometimes, but not because the protocol is inherently quicker. IPv6 traffic often skips carrier-grade NAT, which removes a translation hop and a stateful bottleneck, and major CDNs frequently have better-optimised IPv6 peering. On mobile networks IPv6 can measurably reduce latency. On a well-provisioned fixed line, the difference is usually in the noise.
Privacy differences
Early IPv6 deployments derived the last 64 bits of the address from the device's MAC address, creating a permanent tracking identifier. Modern operating systems use privacy extensions (RFC 4941) that rotate a random interface identifier regularly, so the device portion changes while the network prefix stays stable.
VPN users, take note: if your VPN only tunnels IPv4 and your ISP provides IPv6, websites may still see your real IPv6 address. That is an IPv6 leak. The home page shows both addresses so you can spot a mismatch instantly.
Check your own support
Open the IP checker. If the IPv6 row shows an address beginning with 2 or 3, your connection is dual-stack and working. If it says "Not available", you are IPv4-only — either your ISP has not enabled IPv6, or your router has it switched off in its WAN settings.
Related reading: public vs private addressing and how to hide your IP address.
Frequently asked questions
Do I need to do anything to use IPv6?
Usually not. If your ISP and router support it, your devices configure themselves automatically and prefer IPv6 when a site offers it.
Will IPv4 be switched off?
Not soon. The two run side by side in dual-stack mode, and IPv4 will remain reachable for many years through translation technologies.
Why does my IPv6 address keep changing?
Privacy extensions rotate the device portion of your IPv6 address periodically to make long-term tracking harder. The network prefix from your ISP normally stays the same.
Keep reading
Check any other IP address
Investigating a suspicious login, a spam email header or a server log entry? Run any IPv4 or IPv6 address through the same geolocation and proxy checks.