IPv4 and IPv6 are two versions of the Internet Protocol used to address and route packets between networks. They can carry the same web traffic, but they use different address formats and differ in header design, address space and deployment model.
The core difference
IPv4 uses 32-bit addresses. The original IPv4 specification defines an address as four octets, or 32 bits. RFC 791 is the original specification.
IPv6 uses 128-bit addresses. The current IPv6 specification expands the address size from 32 bits to 128 bits and simplifies parts of the base header. See RFC 8200.
IPv4 example
203.0.113.25
IPv4's limited address space helped drive widespread use of Network Address Translation (NAT), where many devices on a private network share a public address.
IPv6 example
2001:db8:85a3::8a2e:370:7334
IPv6 provides an enormous address space and was designed as the successor to IPv4. IPv6 addresses are commonly shortened by omitting leading zeros and compressing one consecutive run of zero groups with ::.
Does IPv6 make the internet faster?
Not automatically. IPv6 can produce a faster path in one network and a slower path in another because routing, peering, CDN selection, DNS and network configuration matter more than the version number alone. “IPv6 is faster” is therefore not a reliable general rule.
Is IPv6 automatically more secure?
No. IPv6 has modern protocol design and supports security-related extensions, but merely having an IPv6 address does not encrypt web traffic or make a device safe. HTTPS, firewall policy, software updates and correct network configuration still matter. Likewise, NAT in IPv4 should not be treated as a substitute for a firewall.
What is dual stack?
Many networks run IPv4 and IPv6 at the same time. This is called dual stack. A device can therefore have an IPv4 address and one or more IPv6 addresses simultaneously, and a browser may choose either protocol depending on the destination and network conditions.
Why IPv6 matters for VPN testing
If a VPN only changes your IPv4 route while the device still has a usable public IPv6 route outside the tunnel, an IPv6-capable website may see that second address. That is why our VPN Leak Test checks for separate IPv6 exposure instead of assuming the IPv4 result tells the whole story.
How to check which version this connection uses
- Open CheckWhatIsMyIP.
- Look at the public address shown.
- Dots normally indicate IPv4; hexadecimal groups separated by colons indicate IPv6.
- If you use a VPN, run the leak test to check for a second protocol path as well.
IPv4 vs IPv6 at a glance
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32 bit | 128 bit |
| Typical notation | Dotted decimal | Hexadecimal groups |
| NAT | Common | Not required for address conservation |
| Automatic privacy/security | No | No |
Bottom line
IPv6 solves address-space and protocol-design limitations of IPv4, but it is not a magic speed or privacy upgrade. For users, the most useful question is usually not “Which one is better?” but “Which protocol paths does my current network expose, and are they configured correctly?”