IPv4 vs IPv6: what is the difference?
Every device on the internet needs an IP address. For decades, IPv4 has been the standard — but its 4.3 billion addresses are running out. IPv6 was designed to solve this with a virtually unlimited address space. Check your IP to see which version your connection uses.
What is IPv4?
IPv4 (Internet Protocol version 4) was introduced in 1981 and remains the most widely used protocol for routing traffic on the internet. An IPv4 address is a 32-bit number written as four decimal octets separated by dots.
# Example IPv4 address
203.0.113.42
With 32 bits, IPv4 supports approximately 4.3 billion unique addresses. That seemed like more than enough in the 1980s, but with billions of smartphones, IoT devices, and servers now connected, the pool has been exhausted. Regional Internet Registries (RIRs) ran out of new IPv4 blocks between 2011 and 2019.
What is IPv6?
IPv6 (Internet Protocol version 6) is the successor to IPv4, designed to address the shortage of available IP addresses. An IPv6 address is 128 bits long, written as eight groups of four hexadecimal digits separated by colons.
# Example IPv6 address
2001:0db8:85a3:0000:0000:8a2e:0370:7334
With 128 bits, IPv6 supports 340 undecillion addresses (3.4 × 1038). That is enough to assign a unique address to every atom on the surface of the Earth — and still have addresses left over. We will never run out.
Key differences
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address size | 32 bits | 128 bits |
| Format | 192.168.1.1 | 2001:db8::1 |
| Total addresses | ~4.3 billion | ~340 undecillion |
| NAT required | Yes (commonly) | No (end-to-end) |
| Built-in security | Optional (IPsec) | Mandatory (IPsec) |
| Header complexity | Variable length | Fixed, simpler |
Why hasn't everyone switched to IPv6?
The transition has been slow because IPv4 and IPv6 are not directly compatible — they are separate protocols that cannot talk to each other natively. ISPs, companies, and service providers must run both protocols simultaneously (called “dual stack”) during the transition. This requires upgrading routers, firewalls, and software. As of 2026, approximately 45% of global internet traffic uses IPv6, with countries like India, France, and Germany leading adoption above 70%.
Do I have an IPv6 address?
Many connections today support both IPv4 and IPv6 (dual stack). Whether your browser uses IPv4 or IPv6 to reach a site depends on your ISP, your router, and the site itself. Check your IP on heresmyip.com — if the address contains colons (e.g., 2001:db8::1), you are connected via IPv6. If it contains dots (e.g., 203.0.113.42), you are using IPv4.
Does IPv6 affect my privacy?
With IPv4, many devices share a single public IP through NAT, making it harder to identify individual devices. With IPv6, every device can have its own unique global address, which could theoretically make tracking easier. However, modern operating systems use “privacy extensions” (RFC 8981) that rotate the suffix of your IPv6 address regularly, mitigating this concern. Your IP still reveals the same general information regardless of the version — approximate location, ISP, and timezone.