IPv4 vs. IPv6: What's the Difference?

IPv4 and IPv6 are two versions of the Internet Protocol (IP), the system that helps devices identify network destinations and deliver data across interconnected networks. The main difference is their address size: IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses.

This difference gives IPv6 an enormously larger address space, helping the internet accommodate more connected devices and networks. However, IPv6 is not automatically faster or more secure than IPv4, and both versions remain important to everyday internet use.

Understanding these differences can help you troubleshoot network problems, understand public IP addresses, and make more informed decisions about internet privacy.

What Is IPv4?

IPv4, short for Internet Protocol version 4, is a widely deployed version of the protocol used to address and route internet traffic. It specifies how packets carry addressing information so that routers can forward data toward its destination.

An IPv4 address contains 32 bits, conventionally written as four decimal numbers separated by periods. Each number is an eight-bit section called an octet and ranges from 0 to 255.

For example:

• 192.168.1.1 is commonly used as a private address on a local network.
• 8.8.8.8 is an IPv4 address used by Google Public DNS.

Because each of the 32 bits can represent two possible values, IPv4 has 2³², or 4,294,967,296 possible address combinations.

That does not mean all these addresses are available for ordinary public use. Certain ranges are reserved for private networks, loopback communication, multicast, documentation, and other special purposes.

Public and private IPv4 addresses

Many home networks use private IPv4 addresses for devices such as laptops, smartphones, and printers. These addresses allow devices to communicate locally without requiring each one to have its own public IPv4 address.

A router commonly uses Network Address Translation (NAT) to let multiple devices share a public IPv4 address when communicating with the internet.

Private addresses such as 192.168.1.1 are not directly routable across the public internet. Public and private addresses serve different purposes, and neither category automatically determines whether a device is secure.

For more detail, read our guide to public vs. private IP addresses.

What Is IPv6?

IPv6, or Internet Protocol version 6, is the successor to IPv4. It was developed partly to address the limitations of IPv4's relatively small address space and to support continued internet growth.

IPv6 uses 128-bit addresses, giving it 2¹²⁸, or approximately 3.4 × 10³⁸ possible address combinations. That is an enormous expansion over IPv4's theoretical capacity.

IPv6 addresses use hexadecimal notation, which represents values using the digits 0–9 and letters A–F. An address consists of eight 16-bit groups, separated by colons when written in its full form.

For example, the full address 2001:4860:4860:0000:0000:0000:0000:8888 can be shortened to 2001:4860:4860::8888.

How IPv6 address compression works

IPv6 addresses can contain groups consisting entirely of zeros. To make addresses easier to read, leading zeros within a group can be omitted, and one consecutive sequence of zero-valued groups can be replaced with ::.

For example, 2001:0db8:0000:0000:0000:0000:0000:0001 becomes 2001:db8::1. The :: abbreviation can appear only once in an IPv6 address, because using it more than once would make the number of omitted groups ambiguous.

IPv6 provides much more address capacity and includes other protocol changes, such as a simplified base header and support for address autoconfiguration. It does not automatically give every device a permanently exposed address or make every internet connection secure. Address assignment, routing, and firewall rules still matter.

The technical details of IPv6 addressing are defined in the IETF's RFC 4291.

IPv4 vs. IPv6: Key Differences at a Glance

The two protocols perform the same broad role, but they differ in addressing, packet handling, configuration, and compatibility.

These differences are based on the IETF's IPv4 specification, RFC 791, and IPv6 specification, RFC 8200.

One important distinction concerns fragmentation: IPv4 routers may fragment packets when permitted and necessary, whereas IPv6 routers forward packets without fragmenting them. IPv6 relies on Path MTU Discovery and source-side fragmentation when required.

Why Was IPv6 Created?

The internet was originally designed around a much smaller network environment than the one that exists today. As computers, smartphones, servers, connected appliances, and other devices became more common, the demand for IP addresses increased.

IPv4's approximately 4.29 billion theoretical address combinations may sound substantial, but not all of those combinations are available for public allocation. The growth of the internet and the distribution of address ranges among organizations have made public IPv4 addresses a limited resource.

Private addressing and NAT have helped extend IPv4's usefulness. A household can connect many devices using private addresses while sharing one public IPv4 address. Some internet service providers also use Carrier-Grade NAT, allowing multiple customers to share public IPv4 addresses.

However, NAT does not create new globally unique IPv4 addresses. It also introduces complications for certain applications, inbound connections, and network troubleshooting.

IPv6 addresses the underlying capacity problem by providing an enormously larger address space. It also supports structured address allocation and automatic network configuration.

IPv4 exhaustion does not mean that existing IPv4 connections have suddenly stopped working. It concerns the scarcity of unallocated public IPv4 resources, which regional internet registries manage through allocation policies.

IPv6 deployment remains uneven, although it is now a significant part of the internet. Adoption statistics change over time and depend on what is being measured. Measurements of users reaching one provider over IPv6 should not be treated as a universal estimate of every internet connection or website's traffic.

Is IPv6 Faster Than IPv4?

Not necessarily. IPv6 can perform better in some network environments, but there is no universal rule that it is faster than IPv4.

Actual performance depends on several factors:

• Network infrastructure: The quality of the ISP's IPv4 and IPv6 services matters.
• Routing: One protocol may have a more direct or better-optimized route to a destination.
• DNS resolution and connection setup: Name resolution, caching, and application behavior can affect how quickly a connection begins.
• Congestion and latency: Conditions along the network path can affect response times.
• Device and router support: Older or poorly configured equipment may handle one protocol less reliably.
• Destination compatibility: A service must provide an appropriate connection path for the protocol being used.

IPv6's simplified base header can help packet processing in some circumstances, but that does not guarantee smaller packets, lower latency, or faster downloads.

If an IPv6 connection is poorly configured, IPv4 may work better on that network. The most useful comparison is a real test of both paths under similar conditions, not a claim that one protocol is always faster.

Is IPv6 More Secure Than IPv4?

Neither IPv4 nor IPv6 is automatically secure. Both require appropriate network configuration, software updates, firewall rules, and safe application behavior.

IPv6 was designed with support for standardized IPsec security mechanisms. IPsec can provide authentication, integrity, and encryption when the relevant features are correctly configured. However, IPsec can also be used with IPv4, and IPv6 does not automatically encrypt ordinary internet traffic.

IPv6 also changes some common network arrangements. Because IPv6 provides a much larger address space, it reduces the need to share public addresses through NAT. An interface can have a globally routable IPv6 address without being reachable for unsolicited inbound connections when firewall rules block that traffic.

This distinction matters because NAT is not a substitute for a properly configured firewall. NAT may incidentally block some unsolicited inbound traffic in common configurations, but its primary purpose is address translation, not comprehensive security enforcement.

For a safer network:

• Keep routers, operating systems, and connected devices updated.
• Use firewall rules that restrict unwanted inbound connections.
• Avoid exposing network services unnecessarily.
• Check that IPv6 traffic follows the intended firewall and VPN policies.
• Review router and operating-system security settings rather than assuming IPv6 is automatically protected.

The security of an actual connection depends on its implementation and configuration, not simply whether the address begins with an IPv4 or IPv6 format. The IETF's IPsec Security Architecture, RFC 4301, describes security mechanisms that apply to both IP versions.

Can IPv4 and IPv6 Work Together?

Yes. The internet is transitioning gradually, so both protocols coexist. However, they are not directly interchangeable: an ordinary IPv4 packet cannot simply be treated as an IPv6 packet, or vice versa.

Dual stack: A device or network supports IPv4 and IPv6 simultaneously. Applications can use the appropriate protocol based on available connectivity and destination support. This is a common way to maintain compatibility with both older and newer services.

Tunneling: A network encapsulates packets of one protocol inside another protocol to carry traffic across infrastructure that does not natively support the packet's original version. The exact mechanism depends on the deployment.

Translation: Technologies such as NAT64 translate between IPv6 and IPv4 so that IPv6-only clients can communicate with IPv4-only services in supported scenarios. NAT64 is often used with DNS64, which can help clients discover destinations through synthesized DNS responses.

These mechanisms allow gradual deployment without requiring every network, device, and service to upgrade at the same time. For additional technical detail, see the IETF's RFC 6146 on Stateful NAT64.

How to Check Whether Your Device or Network Supports IPv6

A device can have IPv6 enabled without having working IPv6 connectivity to the public internet. Support depends on the operating system, network configuration, router, internet provider, and destination service.

The easiest general test is to open test-ipv6.com in a browser while connected to the network you want to check. The test can help identify whether your current connection provides IPv4, IPv6, or both. Browser extensions, filtering, and firewalls can sometimes interfere with the test.

You can also inspect the addresses assigned to your device.

Windows

1. Open Command Prompt.
2. Enter ipconfig. For more detail, use ipconfig /all.
3. Find your active Wi-Fi or Ethernet adapter.
4. Look for an IPv6 address in its network information.

Microsoft documents these commands in its Windows ipconfig reference. An address beginning with fe80:: is a link-local IPv6 address, used for communication on the local network. Its presence alone does not establish that you can access the IPv6 internet.

macOS

1. Open Apple menu → System Settings → Network.
2. Select your connected network.
3. Open its details and locate the TCP/IP information.
4. Inspect the IPv6 configuration and any assigned IPv6 address.

The exact presentation can vary by macOS version. Apple's IPv6 configuration guide for Mac explains the available settings.

Linux

Open a terminal and run:

ip -6 address show

This lists IPv6 addresses assigned to network interfaces. To display globally scoped addresses specifically, you can also run:

ip -6 address show scope global

If you see only link-local addresses, or no suitable global address, the interface may not have global IPv6 addressing configured. Even a globally scoped address does not, by itself, prove that internet connectivity works. See the Linux ip-address manual page.

Android

1. Open Settings.
2. Go to Network & Internet or the equivalent connections menu.
3. Open Wi-Fi and select your connected network.
4. Inspect the network details for an IP address, where available.

Some devices show both address versions, while others make the information less obvious. For a practical connectivity check, open test-ipv6.com in your browser.

iPhone and iPad

1. Open Settings → Wi-Fi.
2. Tap the information button beside the connected network.
3. Inspect the network details and IPv6 information if displayed.
4. Open test-ipv6.com in Safari to test the active connection.

The settings available depend on the network and operating-system version. The browser test is useful because it checks connectivity rather than merely whether an address appears in a settings screen.

For any platform, test Wi-Fi and mobile data separately if you need to compare them. A successful test on one connection does not guarantee IPv6 availability on another.

Does IPv6 Affect VPNs and Online Privacy?

IPv6 matters to VPN users because a VPN application must handle the types of network traffic that a device can generate.

A VPN leak can occur when traffic that is expected to travel through a VPN instead leaves through the ordinary internet connection. For example, if a VPN protects IPv4 traffic but does not appropriately tunnel or block IPv6 traffic, some IPv6 connections could bypass the intended tunnel.

VPN behavior varies by provider, operating system, VPN protocol, and application configuration. Some VPNs support IPv6 traffic through the tunnel, while others block it or handle it through different mechanisms.

To check your setup, review the VPN provider's documentation and run appropriate leak tests while connected to the VPN. Confirm whether displayed public IPv4 and IPv6 addresses match the behavior you expect from the VPN. A general IPv6 connectivity test is useful, but an IPv6 address appearing in a test is not automatically proof of a leak; its meaning depends on the VPN's documented handling of IPv6.

An IPv6 address also does not automatically reveal your real-world identity. Like an IPv4 address, it can provide information about a network endpoint and may help services estimate a general location or associate activity with a connection. The accuracy and identifiability of that information depend on the address, network, available records, and other contextual data.

A VPN can change the public address that a website sees, but it does not guarantee complete anonymity or prevent all forms of tracking. Read our guide to what a VPN is and how it works for a broader explanation of VPN protection and its limitations.

Should You Use IPv4 or IPv6?

Most ordinary users do not need to choose between IPv4 and IPv6 manually. Their devices and networks can often select the appropriate protocol based on available connectivity and application behavior.

IPv6 is beneficial because it offers a much larger address space and supports modern network deployments. IPv4 remains essential for compatibility with services and networks that have not adopted IPv6.

For most households, the practical goal is a reliable network that supports both protocols where available. Leave network settings at their recommended defaults unless you have a specific troubleshooting reason to change them.

Frequently Asked Questions

Final Thoughts

IPv4 and IPv6 perform the same essential role: helping devices address and route data across networks. The major difference is their capacity. IPv4 uses 32-bit addresses and remains widely supported, while IPv6 uses 128-bit addresses and provides an enormously larger address space for continued internet growth.

Neither version is automatically faster or more secure. Performance and protection depend on the networks, devices, applications, and configurations involved. Both protocols will continue to matter while the internet transitions toward wider IPv6 adoption.

To build on what you've learned, explore our guides to IP addresses, DNS, and VPNs to understand how these technologies work together.