Every device on the internet gets an IP address – it's how data knows where to go. IPv4 is the original system from the 1980s, and IPv6 is its newer, much larger replacement. The short version: you almost certainly don't need to do anything about this. Your ISP and devices handle it automatically. But if you're troubleshooting connectivity issues or just curious about what those long addresses mean, here's what you need to know.

What is IPv4?

IPv4 (Internet Protocol version 4) is the addressing system that's been running the internet since the beginning. IPv4 addresses look like this: 192.168.1.1 – four groups of numbers separated by dots, each ranging from 0 to 255.

The total number of possible IPv4 addresses is about 4.3 billion. That sounded like a lot in the 1980s, but with smartphones, laptops, smart TVs, thermostats, and every other connected device, we ran out. The last blocks of fresh IPv4 addresses were allocated years ago.

To work around this, most networks use NAT (Network Address Translation) – your router gets one public IPv4 address from your ISP, and all your devices share it using private addresses like 192.168.x.x or 10.x.x.x. NAT has kept things working, but it's a workaround, not a real solution.

What is IPv6?

IPv6 (Internet Protocol version 6) is the replacement. IPv6 addresses are much longer and look like this: 2001:0db8:85a3::8a2e:0370:7334 – eight groups of hexadecimal characters separated by colons.

The number of possible IPv6 addresses is roughly 340 undecillion (that's a 3 followed by 38 zeros). Every person on Earth could have billions of addresses and we still wouldn't run out. This eliminates the need for NAT – every device can have its own globally unique address.

Why does IPv6 exist?

The core reason is simple: we ran out of IPv4 addresses. As more devices came online, the 4.3 billion address limit became a real problem. IPv6 solves this with a vastly larger address space.

Beyond just more addresses, IPv6 also simplifies routing (no more NAT complications), has built-in security features, and is more efficient for modern networks. But for most people, the "why" boils down to: we needed more addresses.

Do you need to care?

Mostly no. Here's why:

• Your ISP assigns you addresses automatically, whether IPv4, IPv6, or both
• Your router and devices negotiate which protocol to use without your input
• Most websites and services work on both IPv4 and IPv6
• You don't need to configure anything for day-to-day use

As of 2025, roughly 45-50% of global internet traffic uses IPv6, and that number climbs a few percentage points each year. Most major ISPs run dual stack (supporting both protocols simultaneously), so the transition is happening quietly in the background.

When it actually matters

There are a few situations where IPv4 vs IPv6 becomes relevant:

• Troubleshooting connectivity – if a website or service works for some people but not you, the issue might be IPv4-only or IPv6-only access. Knowing which protocol you're using helps narrow things down
• Hosting a server or game – port forwarding and firewall rules differ between IPv4 and IPv6. If you're setting up a home server, you may need to configure both (see port forwarding)
• IPv6-only ISPs – some mobile carriers and newer ISPs use IPv6 only, with a translation layer (NAT64) to reach IPv4-only sites. This usually works fine, but can occasionally cause issues with older services or games
• Gaming and peer-to-peer – some games and P2P applications connect more reliably over IPv6 because there's no NAT in the way. If you're having trouble with voice chat, multiplayer lobbies, or direct connections, enabling IPv6 might help
• VPN compatibility – some VPNs only tunnel IPv4 traffic, which can cause IPv6 traffic to leak outside the tunnel. Check your VPN's IPv6 support if privacy is a concern

What is dual stack?

Dual stack means your network runs both IPv4 and IPv6 at the same time. Your device gets an address for each protocol and uses whichever one works best for each connection. Most modern operating systems prefer IPv6 when it's available and fall back to IPv4 when it's not.

This is how the transition from IPv4 to IPv6 is actually happening – not a hard cutoff, but a gradual shift where both run in parallel until IPv4 eventually fades out. Most major ISPs and networks already run dual stack.

How to check if you have IPv6

If you're curious whether your connection supports IPv6:

1. Visit test-ipv6.com in your browser
2. The site runs a series of automatic tests and gives you a score out of 10
3. A score of 10/10 means full IPv6 support; 0/10 means IPv4 only

You can also check your current IP addresses:

• Windows – open a terminal and run ipconfig. Look for an "IPv6 Address" entry alongside your IPv4 address
• Mac – open System Settings > Network, select your connection, click Details, and look under TCP/IP for both IPv4 and IPv6 addresses
• Linux – run ip addr in a terminal and look for inet6 entries

If you don't have IPv6 and want it, contact your ISP. It's not something you can enable on your end alone – your ISP needs to support it on their network.

For more about how IP addresses work in general, see Understanding IP Addresses.