IPv4 vs IPv6 - What's the Difference?
IPv4 and IPv6 are the two versions of the Internet Protocol in use today. IPv4, introduced in 1981, uses 32-bit addresses and is running out of space. IPv6, standardized in 1998, uses 128-bit addresses and provides a practically unlimited address pool. Both protocols coexist on most modern networks through a technique called dual-stack.
Side-by-Side Comparison
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Address format | Dotted decimal: 192.168.1.1 | Colon-hex: 2001:0db8:85a3::8a2e:0370:7334 |
| Total addresses | ~4.3 billion (2³²) | ~340 undecillion (2¹²⁸) |
| Address exhaustion | Exhausted globally since 2011 | No exhaustion concern |
| NAT required | Yes, for most home/business networks | No - Every device gets a public IP |
| Header size | 20–60 bytes (variable) | 40 bytes (fixed) |
| Checksums in header | Yes | No - Handled by transport layer |
| IPsec support | Optional | Mandatory (built-in) |
| Autoconfiguration | Requires DHCP | SLAAC - Devices configure themselves |
| Broadcast | Supported | Replaced by multicast |
| Global internet share (2025) | ~60–65% of traffic | ~35–40% of traffic |
IPv6 Address Types
| Type | Prefix | Purpose |
|---|---|---|
| Global Unicast | 2000::/3 | Globally routable - The equivalent of a public IPv4 address |
| Link-Local | fe80::/10 | Auto-assigned on every interface; not routed beyond the local link |
| Unique Local | fc00::/7 | Private addresses (similar to 192.168.x.x); not globally routable |
| Loopback | ::1/128 | Equivalent to 127.0.0.1 in IPv4 |
| Multicast | ff00::/8 | One-to-many delivery; replaces IPv4 broadcast |
| Anycast | From global unicast space | One IP assigned to multiple nodes; nearest responds |
Do You Need to Worry About IPv6?
- Most ISPs now assign IPv6 addresses alongside IPv4 (dual-stack). Your device likely has both already.
- IPv6 removes the need for NAT, so every device can be directly addressable - Firewalls become even more important.
- VPN users should check for IPv6 leaks: some VPNs only tunnel IPv4 traffic, exposing your real IPv6 address.
- Web performance can be better over IPv6 due to the simpler header and removal of NAT traversal overhead.
Why IPv4 Ran Out - And Why It Still Works
IPv4 (RFC 791) was designed in 1981 for a research network, and its 32-bit address field allows about 4.3 billion addresses - Fewer than one per person on earth. IANA handed out its last unallocated IPv4 blocks to the regional registries in 2011, and the registries themselves have since exhausted their general pools.
The workarounds keeping IPv4 alive
- NAT lets a whole household share a single public address - The single biggest reason exhaustion was survivable.
- Carrier-grade NAT (RFC 6598) goes further: ISPs share one public address across hundreds of customers.
- A secondary market exists where organisations buy and sell IPv4 blocks - Scarcity has made addresses a traded asset.
- Dual-stack deployment lets networks run both protocols simultaneously, so neither side notices the transition.
How to read an IPv6 address
An IPv6 address like 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is eight groups of four hexadecimal digits. Two shortening rules apply: leading zeros in each group can be dropped, and one run of consecutive all-zero groups can be replaced by :: - Giving 2001:db8:85a3::8a2e:370:7334. The first 64 bits typically identify the network (your ISP and your home prefix) and the last 64 bits identify the device. Modern operating systems enable privacy extensions by default, rotating the device portion regularly so websites cannot use it as a permanent identifier.
How to Check Whether You Have IPv6
- Open the homepage - If an IPv6 address (containing colons) is shown alongside your IPv4, your connection is dual-stack.
- On Windows, run
ipconfig /alland look for an "IPv6 Address" line that does not start withfe80(that prefix is link-local only, not internet IPv6). - On Mac, check System Settings → Wi-Fi → Details → TCP/IP, where the IPv6 configuration and address are listed.
- If you only ever see IPv4, your ISP or router may not have IPv6 enabled - Many routers have an IPv6 toggle in their WAN settings.
What This Means for You
The IPv4-to-IPv6 transition is designed to be invisible, and for browsing it is - Your device picks whichever protocol works best per connection. Where it becomes visible is in edge cases. Gamers behind carrier-grade IPv4 NAT get strict NAT types that IPv6 avoids entirely. Privacy-conscious users should know that with IPv6 every device has its own globally routable address, so the router firewall - Not NAT - Is what blocks inbound traffic. And VPN users have one concrete action item: if your VPN only tunnels IPv4 while your connection is dual-stack, websites can still see your real IPv6 address. A VPN leak test reveals this in seconds.
Frequently Asked Questions
Is IPv6 faster than IPv4?
Marginally, in some cases. IPv6 has a simpler fixed header and avoids NAT translation overhead, and on some carrier networks it takes a more direct path than CGNAT-burdened IPv4. In practice the difference is usually a few milliseconds - Routing quality matters far more than protocol version.
Should I disable IPv6 to be safer?
Generally no. Disabling IPv6 breaks nothing today but forfeits its benefits and can cause delays on networks that expect it. The realistic security concern is misconfiguration - A router firewall that filters IPv4 but ignores IPv6. Keeping IPv6 on with a properly configured firewall is the better posture.
Will IPv4 ever be switched off?
Not on any announced timeline. Dual-stack operation lets both protocols coexist indefinitely, and too many legacy systems speak only IPv4. What is happening instead is a slow inversion: some mobile and ISP networks are now IPv6-only internally and translate to IPv4 (via NAT64) only when needed.