IPv4 vs IPv6: What's the Difference and Does It Matter?
IPv4 and IPv6 are the two versions of the Internet Protocol. Both give devices an address so they can talk to each other. IPv4 is the original and is running out of space. IPv6 is the newer standard with a far larger pool.
The key differences
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Total addresses | About 4.3 billion | About 340 undecillion (3.4 × 1038) |
| Written as | Decimal, dotted: 192.0.2.1 | Hexadecimal, colons: 2001:db8::1 |
| Address sharing (NAT) | Very common | Rarely needed |
| Typical home subnet | /24 | /64 |
Why IPv6 exists
When IPv4 was designed in the early 1980s, 4.3 billion addresses looked like plenty. Then phones, laptops, TVs and sensors arrived. The central pool of free IPv4 addresses ran out in 2011, and regional registries have since run low too. Providers cope by sharing a single public IPv4 address between many customers using carrier-grade NAT, and by trading existing blocks.
IPv6 solves the shortage outright. It also simplifies routing, removes the need for most address translation and was designed with modern networking in mind.
Are IPv4 and IPv6 compatible?
Not directly. A device that only speaks IPv4 cannot talk to one that only speaks IPv6. In practice most networks run dual stack, which means a device has both an IPv4 and an IPv6 address and uses whichever works best. Your browser usually tries IPv6 first and falls back to IPv4 within a fraction of a second.
Which one am I using?
Open our IP checker. The large address at the top is the one your browser used, and the two lines underneath show whether you also have an IPv4 and an IPv6 address. If IPv6 says “Not detected”, your provider or router probably has not enabled it.
Does it matter for privacy?
A little. IPv6 addresses are so numerous that each device can have its own public address, which could make tracking easier. To limit this, operating systems use privacy extensions that generate temporary, rotating addresses for outgoing connections. If you use a VPN, make sure it handles both versions, otherwise one of them can bypass the tunnel. Our WebRTC leak test can help you spot problems.
Do I need to do anything?
Usually not. If your provider supports IPv6, your router will probably use it automatically. If you run servers, make sure your DNS has both an A record and an AAAA record, and that your firewall rules cover both. See DNS records explained.
Try it yourself
See the real numbers for your own connection with our free tools.