What is IPv4?
IPv4 (Internet Protocol version 4) is the original addressing system that has powered the internet since the early 1980s. It uses a 32-bit address format, written as four groups of numbers separated by dots — a style known as dotted decimal notation.
An example IPv4 address looks like this: 192.168.1.1
Each of the four groups (called octets) can range from 0 to 255, which gives IPv4 a total pool of approximately 4.3 billion unique addresses. That sounded like plenty in the 1980s, but with billions of smartphones, laptops, smart TVs, and IoT devices now online, those addresses have essentially been used up.
What is IPv6?
IPv6 (Internet Protocol version 6) is the next-generation addressing system designed to replace IPv4. It uses a 128-bit address format, written as eight groups of four hexadecimal characters separated by colons.
An example IPv6 address looks like this: 2001:0db8:85a3::8a2e:0370:7334
The double colon (::) is a shorthand that represents one or more groups of consecutive zeros, making the addresses easier to read and write. With 128 bits of address space, IPv6 can support approximately 340 undecillion (3.4 × 1038) unique addresses — a number so vast it is considered virtually unlimited for any foreseeable future.
Key differences at a glance
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address Length | 32-bit | 128-bit |
| Address Format | Dotted decimal | Hexadecimal colon |
| Total Addresses | ~4.3 billion | 340 undecillion |
| Header Size | 20-60 bytes | 40 bytes fixed |
| Security | IPsec available | IPsec available; not automatic |
| NAT Required | Yes, commonly | No, not needed |
| Configuration | DHCP or manual | Auto-configuration (SLAAC) |
Why IPv6 was created
The primary reason for IPv6 is simple: we ran out of IPv4 addresses. The 4.3 billion addresses that seemed more than enough in the 1980s were officially exhausted by regional internet registries starting in 2011. Organizations have relied on workarounds like NAT (Network Address Translation) to stretch the supply, but these add complexity and break the end-to-end connectivity principle the internet was designed around.
At the same time, the explosion of the Internet of Things (IoT) has dramatically increased the demand for IP addresses. Smart thermostats, security cameras, wearables, connected vehicles, and industrial sensors each need their own address. IPv6's enormous address space ensures that every device — present and future — can have a globally unique address without workarounds.
Beyond solving the exhaustion problem, IPv6 brings architectural improvements including a simplified fixed header and stateless address auto-configuration (SLAAC). IPv6 implementations can use IPsec, but ordinary IPv6 traffic is not automatically encrypted just because it uses IPv6.
Do I need to worry about IPv6?
For most everyday internet users, the honest answer is: not really. The transition from IPv4 to IPv6 is happening gradually behind the scenes, and your devices, ISP, and the websites you visit handle the details automatically.
Here's what you should know:
- Your device probably already supports both. Modern operating systems (Windows, macOS, iOS, Android, Linux) have had IPv6 support for years. If your ISP provides IPv6, your device uses it alongside IPv4 without any action on your part.
- Most websites work on both protocols. Major services like Google, Facebook, and Netflix have supported IPv6 for years. If a site only supports IPv4, your connection falls back seamlessly.
- Check IPv6 when you use a VPN. Some VPNs carry IPv4 traffic but leave IPv6 outside the tunnel. Compare the visible IPv6 address and provider with your no-VPN baseline. Learn more in our guide to hiding your IP address.
In short, IPv6 adoption is something network engineers and ISPs worry about. As a regular user, just make sure your privacy tools (like a VPN) cover both versions and you're set.
How to check your IP version
Curious whether you're currently browsing on IPv4, IPv6, or both? The fastest way to find out is to use our free IP lookup tool. It will show you the exact IP address your device is using right now, along with your approximate location and ISP.
Visit our What Is My IP Address page to instantly see your current IP version and details. You can also read our complete IP address guide for answers to common questions about how addresses work.