---
title: IPv4 vs IPv6: what's the difference (and why IPv6 exists)?
description: Every device online needs an address — and we ran out of the old kind. Here's the difference between IPv4 and IPv6, why the switch is happening, and whether you need to care.
canonical: https://watchfor.io/blog/ipv4-vs-ipv6
---

# IPv4 vs IPv6: what's the difference (and why IPv6 exists)?

2026-03-28 · WatchFor Team · Networking · networking, basics

Every device online needs an address — and we ran out of the old kind. Here's the difference between IPv4 and IPv6, why the switch is happening, and whether you need to care.

Every device on the internet needs an **IP address** — a number that says "this is me, send the data here." For decades that number looked like `192.0.2.1`. But the internet grew far bigger than its designers ever imagined, and we literally **ran out of addresses**. Enter IPv6.

If you've seen a weird long address full of colons and hex and wondered what it was, this is the explainer. No deep networking required.

## What an IP address is for

When data travels the internet, it needs a destination — like a postal address for packets. That's the IP address. **DNS** turns a name like `example.com` into one of these addresses (via [A and AAAA records](/blog/dns-record-types-explained)), and the packets find their way there.

There are two versions of these addresses in use today: the old **IPv4** and the newer **IPv6**.

## IPv4: the original (and we ran out)

**IPv4** addresses are **32-bit**, written as four numbers: `192.0.2.1`. That's the format you've seen your whole life.

The problem: 32 bits allows about **4.3 billion** unique addresses. That sounded like plenty in the 1980s. Then came smartphones, laptops, smart TVs, doorbells, fridges… and 4.3 billion stopped being nearly enough. The world has been **out of fresh IPv4 addresses** for years, propped up by clever workarounds (like NAT, where many devices share one public address).

## IPv6: effectively endless

**IPv6** addresses are **128-bit**, written as groups of hex separated by colons: `2001:db8::1`. The longer format unlocks a number so large it's hard to grasp — about **340 undecillion** (that's 3.4 × 10³⁸) addresses. Enough to give every grain of sand on Earth billions of its own.

It's not just more room; IPv6 also brings some efficiency and security improvements baked in. But the headline is simple: **we'll never run out.**

## Side by side

| | IPv4 | IPv6 |
| --- | --- | --- |
| **Size** | 32-bit | 128-bit |
| **Looks like** | `192.0.2.1` | `2001:db8::1` |
| **Total addresses** | ~4.3 billion | ~340 undecillion |
| **Status** | Exhausted (workarounds in use) | The long-term future |
| **Separator** | Dots | Colons |

## How the transition works

You can't flip the whole internet overnight, so most of the world runs **dual-stack**: devices and services speak *both* IPv4 and IPv6 at once. A visitor connects over whichever they support, and adoption of IPv6 keeps climbing year over year. The two will coexist for a long time yet.

## Do you actually need to care?

For most people building websites and apps: **not urgently, but increasingly yes.**

- Your hosting and CDN likely handle IPv6 for you already.
- Some users — especially on mobile networks — connect over IPv6, so supporting it (an **AAAA record** alongside your **A record**) means you're reachable for everyone.
- If you run infrastructure, IPv6 is steadily moving from "nice to have" to "expected."

> **Practical takeaway:** make sure your domain has both an **A** (IPv4) and **AAAA** (IPv6) record if your host supports it, so no visitor is left out.

## A monitoring note

Because both versions are in play, *which* one you check matters. A service can be perfectly reachable over IPv4 but misconfigured on IPv6 (or vice-versa) — so checks default to IPv4, with the option to test IPv6 explicitly where it's supported. If you've added an AAAA record, it's worth confirming it actually works.

## The bottom line

| | In one line |
| --- | --- |
| **IPv4** | The original 32-bit addresses — and we ran out. |
| **IPv6** | 128-bit addresses — effectively unlimited. |
| **Now** | Both run side by side (dual-stack). |
| **You** | Support both (A + AAAA) so everyone can reach you. |

IPv6 isn't exotic — it's just the internet making room to keep growing. You rarely have to think about it directly, but a quick check that your domain works over both versions means you're future-proof and reachable for every visitor.

Inspect a domain's A/AAAA records with the free [DNS lookup](/dns-checker), and learn the records in [DNS record types explained](/blog/dns-record-types-explained).

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Canonical page: https://watchfor.io/blog/ipv4-vs-ipv6 · All articles: https://watchfor.io/blog/all.md · Site guide: https://watchfor.io/llms.txt