What Is an IP Address? A Simple Guide

An IP address is a numerical address used to identify a network connection and help data reach its destination. IP stands for Internet Protocol, the set of rules used to send data across IP networks, including the internet.

Your phone, laptop, router, and the servers behind websites all use IP addresses. An address belongs to a network connection, so it is not a permanent serial number for a device. One device can have several addresses.

How does an IP address work?

When you open a website, your device sends and receives small units of data called packets. Each IP packet includes a source address and a destination address. Routers use the destination to decide where to forward it next. Addressing and forwarding are central to the Internet Protocol specification.

Think of an IP address as a delivery address for network traffic. It helps a packet travel toward the right network and endpoint, but it does not explain what the packet contains.

Opening a website typically involves these steps:

1. Your browser obtains an IP address for the website’s name, often using a cached result or a DNS lookup.
2. Your device sends traffic toward that address through its network connection.
3. Routers forward the packets between networks.
4. The website’s server sends a response that travels back to your device.

The Domain Name System, or DNS, connects names people can remember with addresses computers use. A domain such as byoip.info is a name, not an IP address. ICANN’s explanation of DNS describes this relationship.

What does an IP address look like?

The format depends on the IP version:

In IPv4, each of the four numbers ranges from 0 to 255. IPv6 uses a longer address format that can include the letters a through f as well as numbers. The double colon in an IPv6 address abbreviates consecutive groups of zeros.

Both examples above are reserved for documentation, not live internet use. Those example ranges are defined in RFC 5737 for IPv4 and RFC 3849 for IPv6.

For a comparison of capacity, compatibility, and everyday use, read IPv4 vs IPv6: What’s the Difference?.

What are public and private IP addresses?

A public IP address comes from address space intended for routing on the public internet. A private IPv4 address is used inside a private network and is not globally routable.

For example, your laptop might use 192.168.1.20 at home. Another laptop in an unrelated home can use that same private address. IANA reserves private address ranges specifically so separate networks can reuse them.

A home router commonly uses network address translation, or NAT, to let several devices share a public IPv4 address. That is why an internet IP checker can show a different address from the one in your laptop’s network settings.

Our public vs private IP address guide explains the ranges and how these addresses work together.

What are static and dynamic IP addresses?

These terms describe how an address is assigned:

• A static IP address is configured or reserved to remain the same until the assignment is changed.
• A dynamic IP address is assigned automatically and can change. It does not necessarily change every time a device reconnects.

Many IPv4 networks use DHCP, short for Dynamic Host Configuration Protocol, to give devices addresses and other network settings automatically. DHCP can also deliver a fixed assignment, so automatic configuration does not always mean a changing address. These allocation methods are described in RFC 2131.

A printer can have a fixed private address, while a home connection can have a changing public address. The public/private and static/dynamic distinctions answer different questions.

Who assigns IP addresses?

On a home network, the router usually handles local IPv4 assignments. Your internet service provider supplies the addressing for your internet connection. In a cloud environment, the provider manages assignments to services and workloads.

At a broader level, IANA and the Regional Internet Registries coordinate public address resources. Providers and organizations receive address space through that system, subject to the applicable policies. IANA’s number resources overview explains the hierarchy.

How can you find your IP address?

Start by deciding which address you need:

• For your local network: inspect the details of your active Wi-Fi or Ethernet connection in your device’s network settings.
• For the address a website sees: use an external IP-checking page. It reports the source address used for that connection.

These results can differ because of NAT or a VPN. A VPN can route the website connection through its own exit address. You may also see both IPv4 and IPv6 addresses on the same device.

Why do IP addresses matter for businesses?

An IP address can become part of a customer’s firewall rules, a partner’s access controls, or a service’s DNS configuration. Changing it can mean updating several systems.

Bring Your Own IP, or BYOIP, allows an organization to use an eligible public address range it controls with a supporting provider. It can help preserve addressing when infrastructure changes, subject to the provider’s validation and routing requirements. Read What Is BYOIP? for the next step.

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