IPv4 vs IPv6: what is the difference?

Two formats for internet addresses

IPv4 uses 32-bit addresses, commonly written as four decimal numbers separated by dots. IPv6 uses 128-bit addresses, written as hexadecimal groups separated by colons. IPv6 has a much larger address space.

An IPv6 address can use a double colon to shorten a sequence of zero groups. That shorthand is part of the address format; it does not mean the website has hidden part of the result. IPNIXA allows long addresses to wrap without changing the copied value.

IPv4 and IPv6 at a glance

The two versions do the same job — identifying where traffic should go — but they were designed decades apart.

Your connection may support both

A dual-stack connection supports IPv4 and IPv6. Your browser and network select a working route when visiting a website. Two visits or different services can use different address families even when you stay on the same Wi-Fi.

Modern browsers use a technique called Happy Eyeballs (RFC 8305): when a site has both kinds of address, the browser usually tries IPv6 first and switches to IPv4 within a fraction of a second if IPv6 is slow. That is why a basic lookup on a dual-stack connection often shows only IPv6.

IPNIXA therefore asks two extra test addresses — one reachable only over IPv4, one only over IPv6 — and shows both results. The location and network details come from whichever family your browser used for the main lookup; the network section of the readout tells you which one.

Reading and shortening an IPv6 address

IPv6 addresses look long, but they follow two simple shortening rules. Take the documentation example 2001:0db8:0000:0000:0000:ff00:0042:8329:

1. Split the address into its eight groups of four hexadecimal digits.
2. Drop the leading zeros in every group: 2001:db8:0:0:0:ff00:42:8329.
3. Replace one run of consecutive all-zero groups with a double colon: 2001:db8::ff00:42:8329. The double colon may appear only once in an address.
4. On most networks, the first four groups are the network prefix (/64) assigned by the provider and the last four identify the device’s interface.

How to check whether you have IPv6

A quick check tells you which families your connection actually uses.

1. Open IPNIXA. If “Show IPv6 address” appears under the result, your connection reaches the internet over both IPv4 and IPv6.
2. If the readout says the connection appears to be IPv4-only, check whether IPv6 is enabled in your router’s internet or WAN settings, and whether your provider supports it.
3. Repeat the check on mobile data. Many mobile carriers provide IPv6 even when home broadband does not.
4. If the readout says the connection appears to be IPv6-only, your network reaches IPv4 sites through a translation service; most websites still work normally.

Why IPv6 addresses can change

Devices may use temporary IPv6 addresses to reduce long-term address reuse. A provider can also change the network prefix it assigns. As with IPv4, an address should not be treated as a permanent identity for a person.

Routers and firewalls still matter. A globally routable IPv6 address does not imply that unsolicited incoming connections are allowed, and an IPv4 address behind translation does not by itself prove a network is secure.

What a complete connection test needs

Testing both protocols requires requests to destinations configured to accept each address family separately. A single request to a dual-stack hostname cannot show both outcomes, so IPNIXA checks the other family through a separate Cloudflare test endpoint. The main request address and its metadata appear first, without waiting for that extra test.

If you are troubleshooting a specific application, test that application and consult your provider’s IPv6 documentation. Record the address family along with any error so that support can distinguish a routing issue from a name-resolution or application problem.