What is an IP address?

An IP address is the number that identifies a connection on the internet, so data knows where to go. Every device that goes online uses one.

The short version

When you load a website, your device sends a request saying "please send me this page". The website needs to know where to send the reply, so every request carries a return address. That return address is your IP address. IP stands for Internet Protocol, the set of rules that moves data between networks.

An IP address looks like one of these:

The first is an IPv4 address, the older and still most common format. The second is IPv6, the newer format built to solve a shortage of IPv4 addresses. Many connections now have both. Read about the difference.

Public and private addresses

Most homes and offices actually use two kinds of IP address.

Public IP address

Your internet provider gives your connection a public address. It's the one the rest of the internet sees, and the one shown on our home page. Every device on your home Wi-Fi usually shares it.

Private IP address

Inside your network, your router gives each device its own private address, so it can tell your laptop, phone and TV apart. Private addresses only work inside your network and can be reused in every home. They almost always start with one of these:

• 192.168. (most home routers)
• 10. (common in offices and some routers)
• 172.16. to 172.31.

Your router translates between the two, a process called network address translation (NAT). That's why a website sees your public address and never your private one.

Who hands out IP addresses?

Addresses are allocated in a chain. The Internet Assigned Numbers Authority (IANA) gives large blocks to five regional registries. APNIC is the registry for the Asia-Pacific, including Australia and New Zealand. APNIC allocates blocks to internet providers such as Telstra, Optus and TPG, and they assign addresses to their customers.

Because those allocations are recorded, an address can be linked to the provider that holds it and, roughly, the area where it's used. That's how IP location lookups work.

Why does my IP address change?

Most Australian home and mobile connections have a dynamic IP address. Your provider assigns one from a pool and may give you a different one when your modem restarts, your connection drops, or a lease expires. Mobile data addresses change often, sometimes every time you reconnect.

A static IP address stays the same. Providers usually offer it as an add-on or with business plans. It's useful for running servers, remote access or security rules that allow only certain addresses.

Many providers, especially on mobile networks, also use carrier-grade NAT (CGNAT). That means many customers share a single public IPv4 address at the same time. It's one reason IPv6, which has enough addresses for every device, is being rolled out.

What does my IP address reveal about me?

Less than many people think. From your public IP address, a website can usually tell:

• your internet provider
• your country, which is usually accurate
• a rough city or region, which is often wrong by tens or hundreds of kilometres

It can't tell your name, street address or phone number. Only your provider can link an address to a customer account, and in Australia they release that information only under legal processes such as a court order or law enforcement request.

If you'd rather websites didn't see your real address, a VPN replaces it with the VPN server's address. More on VPNs in the FAQ.