IPv4 vs IPv6: Key Differences Explained Simply
IPv4 uses four numbers and is running out. IPv6 has far more addresses. Here is the difference and whether it matters at home.
IPv4 and IPv6 are two versions of the Internet Protocol, the system that gives devices addresses. IPv4 has been used since the early 1980s and has about 4.3 billion addresses. IPv6 was created because that is nowhere near enough.
IPv4 and IPv6 are two versions of the Internet Protocol. IPv4 has about 4.3 billion addresses and is running out, while IPv6 has far more addresses.
Most homes now run both at the same time. Here is how they differ and what it means for you.
IPv4 vs IPv6 at a glance
| IPv4 | IPv6 | |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Format | 192.168.1.1 | 2001:db8:85a3::8a2e:370:7334 |
| Number of addresses | About 4.3 billion | About 340 undecillion |
| NAT at home | Almost always | Usually not needed |
| Configuration | DHCP or manual | SLAAC, DHCPv6 or manual |
| Router login | 192.168.x.x addresses | Usually still via IPv4 |
I point people at the address-size row first, since it explains why IPv6 exists at all.
Why IPv6 exists
Every phone, laptop, TV and sensor needs an address. IPv4 ran out of new public blocks years ago, so providers rely on tricks like NAT and carrier-grade NAT to share addresses.
IPv6 gives every device its own global address, which simplifies connections for gaming, calls and remote access, and removes the need for address sharing. I stopped worrying about running out of addresses once I understood what IPv6 was for.
Is IPv6 faster or safer?
- Speed: about the same. Some routes are slightly faster on IPv6 because there is no NAT along the way.
- Security: similar overall. Devices have public IPv6 addresses, but your router firewall still blocks unsolicited incoming traffic by default.
- Compatibility: nearly all modern devices and websites support it. Old devices may only speak IPv4.
I tell people to expect the same speed, since the real difference is in how addresses work.
How to check if you have IPv6
- Visit a test site such as test-ipv6.com.
- On Windows, run
ipconfigand look for an IPv6 address that does not start with fe80. - In your router, open the IPv6 or WAN settings to see whether your ISP provides it.
I run the test site first, since it answers the question in seconds.
Should you turn on IPv6 in your router?
If your ISP supports it, yes: leave it on Auto or the setting your provider recommends. Turn it off only to troubleshoot a specific problem, such as a VPN that leaks or an old device that misbehaves.
I leave it on Auto unless something breaks, since that is the setting that causes the least trouble.
What an IPv6 address looks like
IPv4 addresses are four numbers, like 192.168.1.20. IPv6 addresses are much longer and use letters and numbers in eight groups, like 2001:db8:85a3::8a2e:370:7334. The double colon is shorthand for a run of zeros.
- Global addresses usually start with 2 or 3 and are reachable on the internet.
- Link-local addresses start with fe80 and only work on your own network segment.
- Unique local addresses start with fd and work like private IPv4 ranges.
Your device can have several IPv6 addresses at once, including temporary ones that change for privacy. That’s normal. I look at the first group to tell which kind of address it is, since the rest is just length.
IPv6 and gaming, VPNs and CGNAT
IPv6 helps most when your provider uses carrier-grade NAT for IPv4. With IPv6, devices can have proper public addresses again, which can improve NAT types for some games and make remote access possible without port forwarding.
The flip side is that some older VPNs only protect IPv4 traffic and can leak IPv6. If you use a VPN, check it supports IPv6 or blocks it while connected. I check the VPN first when a game lags, since a leak is the usual culprit.
Dual stack: running both at once
Almost every modern network runs IPv4 and IPv6 side by side, called dual stack. Your device uses IPv6 to reach sites that support it and falls back to IPv4 for the rest. You don’t have to choose. If something breaks with IPv6, it’s usually a router or ISP setting, and turning IPv6 off temporarily is a quick test.
I let both run side by side and only turn IPv6 off when I am tracking down a fault.
Turn IPv6 on in your router
- Log in to your router and look for IPv6 settings (often under Advanced or WAN).
- Set the connection type to Auto or the type your ISP uses (often DHCPv6 or SLAAC).
- Save and restart.
- Visit an IPv6 test site to confirm.
If your ISP doesn’t support IPv6 yet, leave it off. Turning it on won’t hurt, but it won’t do anything either. I save and restart before I test, since the setting only takes hold after a reboot.
