IPinfoLabs

IPv4 vs IPv6: What’s the Difference and Which One Am I Using?

Side-by-side comparison of an IPv4 dotted-decimal address and an IPv6 hexadecimal address, with a dual-stack note beneath.

IPv4 vs IPv6: What’s the Difference and Which One Am I Using?

IPv4 and IPv6 are two versions of the Internet Protocol used to address devices on networks. A public IP checker reports the address that reached that checker on that request—which may be IPv4, IPv6, or (on dual-stack networks) whichever path the connection used.

This article explains the practical difference, how to read the formats, and how to tell which one you are using—without treating either protocol as a privacy guarantee.

Direct answer

IPv4 uses 32-bit addresses written as four decimal numbers (for example 203.0.113.10). IPv6 uses 128-bit addresses written as hexadecimal groups separated by colons (for example 2001:db8::1). IPv6 exists because IPv4’s address space is too small for today’s internet. Many networks run both (dual-stack). A “what is my IP” page shows the protocol used for that page load, not a complete inventory of every address your device might have.

What IPv4 is

IPv4 is the original widely deployed Internet Protocol addressing system, specified in RFC 791. An IPv4 address is 32 bits long, which yields about 4.3 billion possible values. That sounded ample in the early internet; it is not enough for every phone, sensor, and virtual machine to have a unique public address.

Because public IPv4 space is scarce, networks commonly share public IPv4 addresses using NAT. That is why a home laptop often has a private IPv4 address while websites see a different public IPv4 address. See public vs private IP addresses.

What IPv6 is

IPv6 is the successor addressing architecture, specified in RFC 8200. An IPv6 address is 128 bits long. That space is large enough that networks can assign global addresses more generously, without relying on IPv4-style NAT for every host.

IPv6 does not mean a device is publicly reachable for unsolicited inbound connections. Firewalls and provider policy still decide what is allowed. A global unicast IPv6 address is still a routing label, not a street address or a person.

How the addresses look

IPv4IPv6
Length32 bits128 bits
Typical writingFour decimal octets: 203.0.113.10Eight hexadecimal groups, with :: compressing zeros: 2001:db8::1
Documentation examplesTEST-NET-3 in RFC 57372001:db8::/32 in RFC 3849
Private / local cousinsRFC 1918 ranges such as 192.168.0.0/16Unique local addresses under fd00::/8 (RFC 4193)

The examples 203.0.113.10 and 2001:db8::1 are documentation addresses, not live public endpoints. If your checker shows a similar pattern with different digits, you are looking at a real assigned address in the same format.

IPv4 uses dotted decimal groups such as 203.0.113.10; IPv6 uses colon-separated hexadecimal groups such as 2001:db8::1. Dual-stack networks can use both.

Why IPv4 ran short—and why IPv6 exists

IPv4’s 32-bit space cannot give a unique public address to every connected device. Regional Internet Registries exhausted freely available IPv4 allocations years ago; remaining IPv4 is reused, transferred, or shared.

IPv6 restores room to number hosts globally. Adoption is uneven: some ISPs and mobile networks prefer IPv6 toward many destinations; some sites and tools still speak IPv4 first. Running both at once is normal, not a misconfiguration.

Public IPv4 vs public IPv6

A public IPv4 address is an internet-facing IPv4 source or destination from globally routed space (not RFC 1918, not loopback, not typical CGNAT shared space). A public IPv6 address in everyday “what is my IP” use is usually a global unicast address—the source that reached the remote service over IPv6.

They are not two spellings of the same number. Dual-stack hosts can have both, and different websites may see different protocols.

Carrier-grade NAT (CGNAT) is mainly an IPv4 sharing technique (RFC 6598 shared address space 100.64.0.0/10). IPv6 does not need that same workaround, but a user can still be on IPv6 toward some sites and shared IPv4 toward others.

How to tell which one you are using

1. Read the address a public checker returns

Open IPinfoLabs (or another checker) and look at the public IP string:

  • Four decimal groups separated by dots → that request used IPv4
  • Hexadecimal groups separated by colons → that request used IPv6

IPinfoLabs shows the public address used for the lookup request. It does not print a separate “IPv4” / “IPv6” badge; the format of the address is the indicator.

2. Remember it is path-specific

The checker reports the source address that reached that service. Another site, or the same site on another network, may use the other protocol. Dual-stack clients often prefer IPv6 when the destination has an AAAA record, but Happy Eyeballs and local policy can still choose IPv4.

3. Compare before assuming a VPN “failed”

If a VPN is IPv4-only, IPv6 traffic might still leave via your ISP unless the VPN client and OS are configured to handle IPv6. A checker that prefers IPv6 could then still show an ISP IPv6 address. That is a dual-stack leak scenario—not proof that IPv6 is “more anonymous.”

4. Check the router only as a second opinion

WAN status pages may list IPv4, IPv6, or both. A WAN IPv4 in 100.64.0.0/10 can disagree with a public checker because of CGNAT. For “what does this website see?”, trust the checker for that website’s path.

Dual-stack, in plain language

Dual-stack means the network can use IPv4 and IPv6. Your phone can have:

  • A private IPv4 address on Wi‑Fi
  • A public IPv4 address (possibly shared) seen by IPv4-only sites
  • One or more IPv6 addresses used toward IPv6-capable sites

None of those facts, by itself, identifies a person. They describe addressing on a path. What an IP address can and cannot reveal covers the privacy limits that apply to both protocols.

NAT still matters on IPv4

IPv4 NAT (more precisely NAPT) lets many devices share one public IPv4 address. IPv6 reduces the need to NAT every host, but mixed networks remain common: IPv6 global addressing plus IPv4 NAT on the same home gateway.

NAT is not a complete firewall, and IPv6 is not “no security.” Policy on the gateway still matters. For the private-vs-public IPv4 picture, stay with public vs private IP addresses.

Common misconceptions

“IPv6 replaced IPv4, so IPv4 is gone.”

No. Large parts of the internet still use IPv4. Many users see both.

“IPv6 is a GPS location.”

No. IPv6 is still an address for routing. Approximate location, when shown, comes from geolocation databases—the same class of estimate as for IPv4. See what IP geolocation is.

“If the checker shows IPv4, I don’t have IPv6.”

Not necessarily. That checker request used IPv4. Your network may still have IPv6 for other destinations.

“IPv6 means websites see my device’s LAN address.”

A global IPv6 address is not the same as an IPv4 192.168.x.x LAN address. It is the source address on that IPv6 path. Firewall policy still applies.

Practical takeaway

  1. Read the format of the address on a public checker.
  2. Treat the result as this request’s protocol, not a full inventory.
  3. On dual-stack networks, IPv4 and IPv6 answers can both be correct.
  4. Use IPinfoLabs to see the public address for the current path, then look up another IPv4 or IPv6 address if you need network context for that address.
  5. ISP and organization labels describe the network association for that address—see what an ISP is.

FAQ

Which is better, IPv4 or IPv6?

Neither is “better” for everyday checking. IPv6 solves address scarcity; IPv4 remains widely used. What matters for a checker is which protocol that connection used.

Can I look up both IPv4 and IPv6 on IPinfoLabs?

Yes. Manual lookup accepts globally assigned IPv4 and IPv6 addresses. Private, reserved, or otherwise unsupported inputs may be rejected. The dashboard shows one result at a time—the address you detected or looked up.

Does IPv6 hide me from my ISP?

No. Your ISP still provides the connection. A VPN can change the source address sites see for tunneled traffic; it does not erase accounts, cookies, or ISP assignment records.

Why do two “what is my IP” sites disagree?

They may prefer different protocols, sit on different networks, or see you through a VPN, proxy, or CGNAT path. Compare the format of each result and whether you were on the same network.

References