What Is an IP Address? IPv4 vs IPv6 Explained

TL;DR

• An IP address is a number that identifies a device on a network that uses the Internet Protocol, so data knows where to go.
• IPv4 addresses are 32 bits long (like 192.0.2.1). IPv6 addresses are 128 bits long and exist because IPv4 addresses are limited in number.
• Private addresses work only inside a local network, such as your home Wi-Fi. A public address is the one the wider internet sees.
• Addresses are usually handed out automatically, and many change over time.

What an IP address is #

"IP" stands for Internet Protocol. An IP address is a number that identifies a device on a network that uses that protocol [1]. When you load a web page, data is sent to your address so it reaches your device and not someone else's. It works a bit like a postal address: without it, the delivery has nowhere to go.

People rarely type these numbers. Instead they use names, and the Domain Name System looks up the matching address [5].

IPv4 vs IPv6 #

There are two versions in use today.

IPv6 was created because the IPv4 space is limited. It increases the address size from 32 to 128 bits, which allows far more devices and more levels of structure [2]. It also simplifies some of the packet header and makes automatic setup easier [2]. Most networks run both versions side by side for now.

Public vs private addresses #

A public address is one that other networks on the internet can send traffic to. A private address is only meaningful inside one network. Standards reserve three blocks of IPv4 space for private use [3]:

• 10.0.0.0 to 10.255.255.255
• 172.16.0.0 to 172.31.255.255
• 192.168.0.0 to 192.168.255.255

Anyone can use these ranges without asking, which is exactly why they save public addresses: your home network and a stranger's can both use 192.168.1.x at once, because the addresses only have to be unique inside each network [3]. Private hosts reach the internet through a gateway, in a home this is your router [3]. To the outside world, all your devices appear to come from the router's public address.

This is also why your phone shows a different address on Wi-Fi than a "what is my IP" website does. One is the private address inside your home, the other is the public one.

How an address is assigned #

On most networks nobody types addresses in by hand. A protocol called DHCP lets a device ask a server for one automatically: the device calls out, the server offers an address, the device accepts, and the server confirms [4]. The address is leased for a limited time and can be renewed or reused by another device later [4]. That is why many home addresses are "dynamic" and can change. A fixed ("static") address is simply one that is configured not to change.

FAQ #

Does an IP address show my exact location? #

Not exactly. An address usually identifies a network and its provider, so tools can only guess a rough area. It does not give your street address.

Can I hide my IP address? #

Tools such as a VPN make websites see a different public address, but they do not make you anonymous.

Why are we running out of IPv4 addresses? #

A 32-bit address allows only about 4.3 billion combinations, which is not enough for every connected device to have its own public address. IPv6 and private address ranges both help with this [2][3].

Is my IP address the same as my Wi-Fi password or my device name? #

No. It is only a network label. Passwords control who may join the network, and names are a convenience.

Sources #