IPv4 vs IPv6 — What's the Difference?

IPv4 and IPv6 are the two addressing standards that identify devices on the internet. Every device gets an address from one or both of them, and knowing which one you're using matters for networking, VPNs and debugging.

What is IPv4?

IPv4 uses a 32-bit address, written as four decimal numbers separated by dots — for example 8.8.8.8 or 192.168.1.1. It was deployed in the early 1980s and supports about 4.3 billion unique addresses. Because the internet grew far beyond that, IPv4 address space ran out and gave rise to NAT and shared addressing.

What is IPv6?

IPv6 uses a 128-bit address, written as eight groups of four hex digits separated by colons — for example 2606:4700:4700::1111 (consecutive zero groups are shortened with ::). It provides an effectively unlimited pool of addresses, includes built-in security (IPsec) and simplifies routing.

Key differences

• Format: dotted decimal (IPv4) vs. colon-separated hexadecimal (IPv6)
• Length: 32 bits vs. 128 bits
• Capacity: ~4.3 billion vs. ~340 undecillion addresses
• Header: simple vs. more efficient, extensible
• NAT: widely needed vs. usually unnecessary

How to tell whether your IP is IPv4 or IPv6

The quickest way is to open ip.ls in a browser — your current address is shown with its family label, and the IPv4 / IPv6 rows fill in accordingly. From a terminal, run:

curl ip.ls

If the result contains colons (:) it is IPv6; if it is four dotted numbers, it is IPv4. The dedicated single-stack probes 4.ip.ls and 6.ip.ls force each family so you can verify both.