What Is an IP Address?

Every packet crossing the Internet carries two addresses—where it came from, and where it's going. Without these coordinates, the data is lost. With them, information finds its way home across billions of devices.

Identity and Location in Four Numbers

An IP address does two things at once: it identifies your device and locates it within the network. Think of how a street address works—"742 Evergreen Terrace" tells you both what (that specific house) and where (that location in Springfield).

The most common format is IPv4: four numbers between 0 and 255, separated by dots. 192.168.1.1 or 172.16.254.1. These 32 bits encode approximately 4.3 billion unique addresses—each one a coordinate in digital space.

You can see your own at Connected's What Is My IP Address tool.

The Envelope System

When you request a webpage, the data doesn't arrive as one continuous stream. It's broken into packets—small envelopes of information. Each packet's header contains the source IP (yours) and the destination IP (the server).

Routers read these addresses like postal workers reading envelopes. They don't care what's inside. They look at the destination, consult their routing tables, and forward the packet along the most efficient path. When it arrives, the server reads your source IP to know where to send the response.

This happens in parallel for thousands of packets, each finding its own route, sometimes arriving out of order. Higher-level protocols reassemble them—the addressing system just gets them there.

Two Kinds of Addresses

Public IP addresses are globally unique. Your Internet Service Provider assigns one to your home network. This is what the world sees—your network's face to the Internet.

Private IP addresses live inside your local network. Your router assigns them to your laptop, phone, smart TV. They're not routable on the Internet—by design. Addresses starting with 192.168, 10, or 172.16-172.31 are reserved for private use.

Your router acts as translator. When your laptop (private IP: 192.168.1.5) requests a webpage, the router replaces that address with your public IP before sending it out. When the response returns, the router remembers which device asked and forwards it to the right private address.

This is Network Address Translation—the reason your entire home can share one public IP address.

A Packet's Journey

You're in New York. You click play on a video hosted in Tokyo.

Your laptop (192.168.1.5) sends a request to your router. The router forwards it to the Internet, stamped with your public IP (203.0.113.45). The packet hops through dozens of routers—New York to Chicago to San Francisco to Tokyo—each one reading the destination and choosing the next hop.

The Tokyo server receives it and sends video data back to 203.0.113.45. Your router receives thousands of packets and distributes them to 192.168.1.5. The video plays.

All of this in fractions of a second. All because each packet carried two addresses.

The Address Crisis

In 1981, 4.3 billion addresses seemed inexhaustible. By 2011, they were gone.

On February 3, 2011, the Internet Assigned Numbers Authority allocated the last free blocks of IPv4 addresses. The well had run dry.

IPv6 was already waiting—128-bit addresses providing 340 undecillion possibilities (3.4×10³⁸). Enough to assign thousands of addresses to every grain of sand on Earth. Yet as of 2025, IPv4 still carries most Internet traffic.

Why? Network Address Translation extends IPv4's life. Your home router lets dozens of devices share one public address. The shortage forced efficiency rather than collapse.

But the fundamental insight remains: you can't send data to somewhere without knowing where somewhere is.

The Coordinates of Connection

Without addresses, there is no Internet—just isolated machines with no way to find each other.

With addresses, every device on Earth can reach every other device. A laptop in New York can request bytes from a server in Tokyo, and both know exactly where to send and where to listen. That's not just infrastructure. That's what makes connection possible.

Check your own coordinates: What Is My IP Address