IPv4 vs IPv6: Differences That Matter
IPv4 uses 32-bit addresses and has a limited address space, while IPv6 uses 128-bit addresses and was designed to support vastly more devices and simpler end-to-end addressing. Most modern internet services need to handle both during a long dual-stack transition.
Address size and notation
IPv4 addresses contain 32 bits and are usually written as four decimal numbers, such as 203.0.113.10. IPv6 addresses contain 128 bits and use hexadecimal groups separated by colons, such as 2001:db8::10. IPv6 notation allows zero compression, which is why two colons can appear in a valid address.
Why IPv6 exists
The IPv4 address space is limited. Techniques such as NAT and carrier-grade NAT extended its practical life, but they also introduced address sharing and additional translation layers. IPv6 provides an enormous address space and was designed as the long-term successor to IPv4.
NAT is not the same as a firewall
Many people associate IPv4 NAT with security because unsolicited inbound connections are often blocked by consumer routers. The security boundary, however, comes from firewall policy—not from address translation itself. IPv6 networks should use appropriate stateful firewall rules even though devices can have globally routable addresses.
Privacy addresses and multiple IPv6 addresses
An IPv6 device can have several addresses at once: link-local addresses, stable addresses and temporary privacy addresses are common. Seeing multiple IPv6 addresses on a laptop or phone is therefore normal. Temporary addressing is designed to reduce long-term correlation based on a single interface identifier.
DNS and dual stack
DNS commonly uses A records for IPv4 and AAAA records for IPv6. A dual-stack service publishes both and lets clients choose the usable path. Operationally, this means monitoring, logging, rate limiting and security tools must correctly handle both address families.
What businesses should test
- Does the website and CDN accept IPv6 clients?
- Do application logs store full IPv6 addresses without truncation?
- Do rate limits understand IPv6 prefixes rather than treating every temporary address as unrelated?
- Do firewalls and allowlists contain equivalent IPv4 and IPv6 rules?
- Do fraud and IP-intelligence vendors provide useful IPv6 coverage?
- Do analytics and support tools display IPv6 correctly?
IP lookup differences
The same lookup concepts apply to both protocols—country, ASN, provider, hostname and risk signals—but data quality can differ by network and provider. IPWander accepts both formats. Use how to find your IP address if you want to see which addresses your device currently has.
Look up an IP address
Check approximate location, network ownership and privacy/risk signals.