What is an IP Address?

Every device that connects to a network needs an address. Without one, there is no way to send data to the right place. An IP address is that address: a unique numerical label assigned to every device on a network so that data knows where to go and where it came from.

Your phone has one. Your laptop has one. The website you are reading right now has one. Even your router has two: a public IP assigned by your internet service provider that faces the open internet, and a private IP like 192.168.1.1 that faces your local home network.

How IP Addresses Work

An IP address functions like a postal address for the internet. When you send a letter, the postal system reads the address on the envelope to figure out which country, city, street, and building it should go to. IP addresses work the same way for data.

When you load a webpage, your device sends a request that includes two IP addresses: the source (your device) and the destination (the web server). Routers along the way read the destination IP address and forward the packet one hop closer, the same way sorting facilities route a package across the country.

You never type an IP address to visit a website, though. You type something like google.com. That is where DNS (Domain Name System) comes in. DNS is the phone book of the internet. When you type a domain name into your browser, a DNS server translates it into the corresponding IP address (say, 142.250.80.46) and your device sends the request there.

Every time you load a page, stream a video, or send a message, hundreds of data packets fly across the internet with IP addresses stamped on them, getting routed through dozens of networks to reach the right machine.

IPv4 Address Structure

The IP address format most people recognise looks like this: 192.168.1.1. This is IPv4, and it has been the backbone of the internet since 1981.

An IPv4 IP address is a 32-bit number, meaning 32 ones and zeros in binary. Since nobody wants to read binary, we write it as four decimal numbers separated by dots. Each number is called an octet (because each represents 8 bits), and each can range from 0 to 255.

The lowest possible IPv4 address is 0.0.0.0 and the highest is 255.255.255.255. That gives about 4.3 billion unique combinations. In the 1980s, 4.3 billion addresses seemed like more than enough. It was not.

Every IPv4 IP address has two parts: the network portion and the host portion. The network portion identifies which network the device belongs to, and the host portion identifies the specific device on that network. A subnet mask determines where the split happens. For a typical home network with a subnet mask of 255.255.255.0, the first three octets (like 192.168.1) identify the network, and the last octet (like .1 or .100) identifies the individual device.

This structure is what lets routers efficiently forward traffic. They only need to look at the network portion of the IP address to decide which direction to send a packet.

Public vs Private IP Addresses

Not all IP addresses are created equal. Some IP addresses are visible on the open internet. Others exist only inside your home or office network. This is the split between public and private IP addresses.

Your ISP assigns your router a single public IP address. This is the address that websites see when you visit them. It is globally unique. No other device on the internet has the same one at that moment.

Behind your router, every device gets a private IP address. Your router assigns these automatically using DHCP. These private addresses come from three ranges reserved by a standard called RFC 1918, and they only work within your Local Area Network (LAN):

• 10.0.0.0 to 10.255.255.255 (16.7 million addresses)
• 172.16.0.0 to 172.31.255.255 (1 million addresses)
• 192.168.0.0 to 192.168.255.255 (65,536 addresses)

The most common home network range is 192.168.x.x. These IP addresses cannot be reached from the internet directly. They only work within your local network.

So how does your laptop, with a private IP address like 192.168.1.100, communicate with a web server on the internet? Through NAT (Network Address Translation). Your router swaps your private IP for its public IP on outgoing traffic, and reverses the swap on incoming responses. This is why hundreds of millions of home networks can all use 192.168.1.x internally without conflicts.

How Your Router Uses IP Addresses

Your router is the central hub of your home network’s IP address system. The router plays three roles when it comes to addressing.

First, it is the default gateway. This means it is the exit door for any traffic leaving your local network. Every device on your network knows: “If I need to reach something outside this network, send it to the router.” The router’s local IP address, commonly 192.168.1.1, is that gateway address.

Second, it is the DHCP server. When your phone connects to Wi-Fi, it does not have an IP address yet. It sends a broadcast asking for one, and the router responds with an available IP address from its pool. The router might assign your phone 192.168.1.100, your laptop 192.168.1.101, and your smart TV 192.168.1.102. It keeps track of which IP address belongs to which device.

Third, it handles NAT. When your laptop sends a request to load a website, the router replaces the source IP address (192.168.1.101) with its own public IP, forwards the request to the internet, and when the response comes back, it sends it to the right device internally.

This whole system is invisible when it works. You connect to Wi-Fi and everything has an IP address.

IPv6: The Next Generation

IPv4’s 4.3 billion IP addresses ran out. The global pool of unallocated IPv4 addresses was exhausted in 2011. Regional registries have been rationing their remaining blocks ever since. The internet grew far beyond what the original designers anticipated.

IPv6 is the solution. Instead of 32 bits, an IPv6 IP address uses 128 bits. That produces 340 undecillion unique addresses, a number so large it is effectively infinite. Written out, an IPv6 address looks quite different from IPv4:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

It uses eight groups of four hexadecimal digits, separated by colons. Leading zeros can be dropped, and consecutive groups of zeros can be replaced with ::, so the address above can be shortened to 2001:db8:85a3::8a2e:370:7334.

Adoption has been gradual. Most of the internet runs on both IPv4 and IPv6 simultaneously, a setup called dual-stack. Your ISP may already assign you an IPv6 address alongside your IPv4 one. Google reports that over 45% of connections to its services now use IPv6.

For home users, IPv6 mostly works in the background. Your router and operating system handle it automatically. But IPv6 changes some fundamentals: with enough IP addresses for every device to have a globally unique one, the need for NAT and private address ranges may eventually disappear.

Finding Your IP Address

You have two IP addresses to find: your public IP address (the one the internet sees) and your private IP address (the one your local network uses).

For your public IP, the fastest method is a what is my IP tool. Visit any such tool and it displays your public IPv4 (and often IPv6) address instantly. This is the IP address your ISP assigned to your router.

For your private IP address, the method depends on your operating system:

• Windows: Open Command Prompt and type ipconfig. Look for “IPv4 Address” under your active network adapter.
• macOS: Open Terminal and type ipconfig getifaddr en0 (for Wi-Fi) or check System Settings > Network.
• Linux: Open Terminal and type ip addr or hostname -I.
• iPhone/Android: Check your Wi-Fi connection details in Settings.

To find your router’s IP address (the default gateway), the same commands work. On Windows, look for “Default Gateway” in the ipconfig output. On macOS and Linux, use ip route | grep default or netstat -rn. This is typically 192.168.1.1 or 192.168.0.1.

For a detailed walkthrough, see our guide to finding your router IP address.