IPv4 (Internet Protocol version 4) and IPv6 are two versions of the addressing system that identifies devices on the internet. IPv4 has been the standard since 1983. IPv6 was introduced in 1998 to replace it as IPv4 addresses ran out.
Side-by-Side Comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Format | Four decimal numbers (0-255) separated by dots | Eight groups of four hex digits separated by colons |
| Example | 203.0.113.42 | 2001:0db8:85a3::8a2e:0370:7334 |
| Address space | ~4.3 billion | ~340 undecillion |
| Header size | 20 bytes minimum | 40 bytes fixed |
| NAT required | Usually (addresses ran out) | No (enough for every device) |
| Built-in security | Optional (IPsec) | Mandatory (IPsec) |
Should You Be on IPv4 or IPv6?
Most ISPs now support both simultaneously using a technique called dual-stack. Your device will prefer IPv6 when available because it is more efficient. You do not need to choose - your connection handles it automatically.
Why Is IPv6 Not Fully Adopted Yet?
Many older routers, firewalls, and enterprise systems still do not fully support IPv6. ISPs needed to upgrade infrastructure, and many took years to roll it out. Adoption has accelerated since 2016 and is now above 45% globally.
People Also Ask
- Is IPv4 still used today?
- Yes, IPv4 remains the majority of internet traffic. Most websites support both IPv4 and IPv6, but IPv4 is still how most connections are made in 2026.
- What is IPv6 used for?
- IPv6 provides a unique address for every device on the planet. IoT devices, mobile networks, and modern ISPs are the biggest users of IPv6 today.
Related: What is an IP address? | Check your IPv6