What is an IP address?

An IP address is the number that identifies a device on a network so that data can find its way to it and back. Every time you load a page, your request carries your IP address as the “return to sender” field, and the server sends its reply there. Without it, the internet would have no way to route anything.

IP stands for Internet Protocol, the set of rules that splits data into packets and stamps each one with a source and a destination address. Routers between you and the server read only that address and forward the packet one hop closer. They don’t need to know what is inside.

You can see the address the internet sees for you right now on the What is my IP page.

What an IP address looks like

There are two versions in use today, and they look nothing alike.

IPv4 addresses are four numbers from 0 to 255, separated by dots:

203.0.113.42

Each number is one byte, so an IPv4 address is 32 bits long. That allows about 4.3 billion unique addresses, which sounded like plenty in 1981 and turned out not to be.

IPv6 addresses are 128 bits long and written as eight groups of hexadecimal digits separated by colons, with runs of zeros shortened to :::

2001:db8:85a3::8a2e:370:7334

IPv6 has room for about 3.4 × 10³⁸ addresses, enough that every device can have its own globally unique one. Many connections now have both. The details are in our guide to IPv4 vs IPv6, and the IPv6 test tells you whether yours works.

Public and private addresses

Your laptop, phone and TV almost certainly do not have their own public IPv4 address. Instead, your home uses two layers:

• Private addresses inside your network, handed out by your router. They are only meaningful on your local network, so millions of homes reuse the same ones.
• One public address on the router’s internet side. Every device in your home shares it when talking to the outside world.

The router keeps track of which internal device opened which connection and rewrites the addresses on the way out and back in. This is called NAT (network address translation), and it is the main reason IPv4 has lasted as long as it has.

A few ranges are reserved for special uses, which helps you recognise what you are looking at:

If your router’s settings page shows a WAN address in the 100.64.x.x range, or an address that doesn’t match what our My IP tool reports, your provider is using carrier-grade NAT: you share a public address with other customers. That is common on mobile networks and some fibre and cable providers, and it is why hosting a game server or opening ports from home sometimes doesn’t work.

How your devices get an address

When a device joins your Wi-Fi, it asks the router for an address using DHCP (Dynamic Host Configuration Protocol). The router picks a free private address, tells the device which address to use as the gateway and which DNS servers to ask, and leases it for a set time.

Your router gets its public address from your internet provider in much the same way. The provider owns blocks of addresses, assigned by one of the five regional internet registries (ARIN, RIPE NCC, APNIC, LACNIC and AFRINIC), and lends one to your connection.

On IPv6, devices usually configure themselves: the router announces the network prefix and each device builds its own address from it, a process called SLAAC.

Static vs dynamic

• A dynamic address can change: after a router restart, when the lease runs out, or whenever the provider reshuffles its pool. This is the default for home and mobile connections.
• A static address stays the same. Businesses pay for one when they run servers, VPN gateways or allow-lists that need a fixed address.

If a site you use keeps asking you to re-verify your login, a changing IP address is one possible reason.

What your IP address reveals, and what it doesn’t

Your public IP address is visible to every website and service you connect to. It is also personal data under the GDPR, because combined with your provider’s records it can identify a subscriber. Here is what someone can realistically learn from it:

Location from an IP address comes from databases that map address blocks to places. These databases are built from registry records, provider data and measurements, and they are approximate. Mobile and carrier-grade NAT addresses are often placed in the city where the provider’s equipment sits, which can be hundreds of kilometres from you. That is why our tools label location as an estimate.

The one party that can tie an address to a specific customer is the internet provider, and it normally does so only for law enforcement or under a court order.

How to find your IP address

Your public IP address (the one websites see): open What is my IP. It shows your IPv4 and IPv6 address, provider and approximate location. In a terminal or script, the IP API returns just the address as plain text or JSON, with ready-made examples for curl, Python, JavaScript, PHP and Go.

Your private IP address (inside your network):

• Windows: run ipconfig and look for “IPv4 Address”.
• macOS: System Settings → Network → your connection → Details. Or run ipconfig getifaddr en0.
• Linux: run ip addr or hostname -I.
• iPhone / Android: open the Wi-Fi settings and tap the connected network.

To look up who owns some other address, for example one you found in an email header or a server log, an IP lookup queries the regional registry for the owner and network range.

Can you hide your IP address?

You can’t browse without an IP address, but you can make sites see a different one:

• VPN: your traffic goes through the VPN provider’s server, so sites see its address. You are trusting the VPN provider instead of your ISP.
• Tor: your traffic hops through three volunteer relays. Slower, but no single relay knows both who you are and where you are going.
• Private Relay and similar browser features: they hide your address from websites in specific apps (Safari, for example) while keeping a rough location.

Our My IP page is a quick way to check that a VPN is working: the address and provider shown should be the VPN’s, not your home provider’s. If your IPv6 address still shows your real provider, the VPN isn’t covering IPv6 and you have a leak.

In short

• An IP address is the routing address for a device on a network.
• At home, your devices have private addresses and share one public address through the router.
• The public address reveals your provider and a rough location, not your identity.
• It can change, and that is normal.