What is an IP address? Your device's internet address

An IP address is the number that identifies a device or network on the internet, so that data knows where to go, like the address on an envelope. IP stands for Internet Protocol, the shared rules for sending data in small packets. Every packet carries two addresses, where it's from and where it's going, and the routers that pass it along read only those to move it toward its destination.

In short

• An IP address is a delivery address for data. Older IPv4 addresses look like 203.0.113.42; newer IPv6 ones are much longer.
• Your devices at home usually share one public address; the router gives each a private one and keeps track of who asked for what.
• Your public address reveals your internet provider and a rough area, not your street or your name.

What does an IP address do?

When you load a web page, your device splits its request into packets, each stamped with the server's IP address as the destination and your address as the return address. Routers along the way, run by your provider and many other networks, read the destination, look it up in their tables and send the packet one hop closer. The server's reply comes back the same way, addressed to you. That is the whole job: getting packets from one numbered place to another across the internet.

People rarely type IP addresses, because the internet's naming system, DNS, turns names into numbers. When you type a website's name, your device first asks DNS for its IP address and then connects to that number. The same lookup tells a mail server where to deliver mail, which is how email finds its way.

What's the difference between IPv4 and IPv6?

The original version, IPv4, was defined in RFC 791 in September 1981. Its addresses are 32 bits long, written as four numbers from 0 to 255 separated by dots, such as 203.0.113.42. Each of the four numbers is one byte, so the whole address is just one number between 0 and 4,294,967,295.

That gives 2 to the power 32, about 4.3 billion addresses: generous for a research network in 1981, and only about one for every two people alive today. The central pool ran dry first. On 3 February 2011, according to the Number Resource Organization, the global registry handed out its last blocks of IPv4 addresses to the five regional registries, which then ran out in turn over the following years. IPv4 addresses are now bought, sold and leased between organizations.

IPv6, defined today in RFC 8200, uses 128-bit addresses, written as eight groups of hexadecimal digits separated by colons, such as 2001:db8:85a3::8a2e:370:7334 (a double colon stands for a run of zeros).

	IPv4	IPv6
Length	32 bits	128 bits
Looks like	203.0.113.42	2001:db8::1
Number of addresses	About 4.3 billion	About 340 undecillion: 34 followed by 37 zeros
First defined	1981	1995, with the current version in 2017
Address sharing	Common, through NAT (see below)	Rarely needed: every device can have its own

The two don't talk to each other directly, so the internet runs both side by side, and the switch has taken decades. According to Google's measurements, reported by the Internet Society, the share of users reaching Google over IPv6 first passed half, 50.10%, on 28 March 2026.

Why do the devices in my home share one address?

Because of IPv4's shortage, most homes get a single public IPv4 address from their provider, and the router shares it. Inside the home, the router hands each device a private address from ranges set aside for that purpose in RFC 1918: addresses starting 10., 172.16. to 172.31., or 192.168. These ranges can be reused in every home and office in the world because they never travel on the public internet. Connect a phone to Wi-Fi and the router assigns it one, often something like 192.168.1.23, automatically.

The trick that lets them share is called network address translation, NAT. Each connection also carries a port number, a sort of apartment number within an address, and the router uses it to keep track of who asked for what. Follow a laptop and a phone at home, sharing the public address 203.0.113.42:

Step	From	To	What the router does
Laptop sends a request	192.168.1.23, port 52144	A web server	Swaps the private address for its public one: 203.0.113.42, port 61001. Notes the pairing.
Phone sends a request	192.168.1.40, port 50310	The same server	Swaps it for 203.0.113.42, port 61002. Notes that pairing too.
Server replies to port 61001	The web server	203.0.113.42, port 61001	Looks up its notes: 61001 means the laptop. Delivers to 192.168.1.23.
Server replies to port 61002	The web server	203.0.113.42, port 61002	61002 means the phone. Delivers to 192.168.1.40.

To the server, both devices look like one address. That is also why a server can't usually connect to a device at home unprompted: the router has no note saying where to send it, so it drops it. Many mobile providers go a step further and put thousands of customers behind one shared public address.

Does my IP address reveal where I live?

Less than many people fear, and more than nothing. Your public IP address is visible to every website and service you connect to; it has to be, or replies couldn't reach you. From it, anyone can look up which provider the address belongs to, and commercial databases estimate a location. Those estimates are rough. MaxMind, a major provider of such databases, reports on its accuracy page that for the United States it places about 60% of addresses within 50 kilometers of their true location, and the rest farther off or not at city level at all. An IP address commonly points to a city or a provider's hub, sometimes the wrong one, not a street or a house.

What links an address to you personally is your provider's records of which customer held that address at a given time. Providers generally hand those over only under legal process, such as a court order, which is how police investigations trace an address to a person. Many home addresses also change from time to time, as providers reassign them.

An IP address can show	It can't, on its own, show
Your internet provider	Your name
A rough area, often a city or region	Your street or house
That several visits came from the same network	Which person in the household made them
Whether you seem to be using a VPN or a data center	What you did inside encrypted connections

To hide your address from the sites you visit, a VPN sends your traffic through its own server, so sites see the VPN's address instead. That moves the trust rather than removing it: the VPN provider now sees your real address.

Check yourself

• Without looking back: why did IPv4 run out, and what does IPv6 change?
• How does a router with one public address get replies back to the right device at home?
• What can a stranger learn from your IP address, and what would they need your provider for?

Sources

• Internet Protocol, RFC 791 — Information Sciences Institute for DARPA, IETF, 1981
• Internet Protocol, Version 6 (IPv6) Specification, RFC 8200 — Internet Engineering Task Force, 2017
• Address Allocation for Private Internets, RFC 1918 — Internet Engineering Task Force, 1996
• Free pool of IPv4 address space depleted — Number Resource Organization, 2011
• 18 years later, IPv6 reaches majority — Internet Society Pulse, 2026
• GeoIP accuracy comparison — MaxMind