An IP address is the number that identifies a device on a network, so that data sent to it arrives in the right place. Every website, phone, laptop and router online uses one. People rarely type them, because domain names exist to stand in for them.
The two formats: IPv4 and IPv6
IPv4 addresses are four numbers from 0 to 255 separated by dots, such as 203.0.113.7. They are 32 bits long, which allows about 4.3 billion addresses, far fewer than the number of devices now online. IPv6 was designed to fix that shortage. Its addresses are 128 bits, written as groups of hexadecimal digits separated by colons, such as 2001:db8::1, where a double colon stands for a run of zeros. Most networks today run both side by side.
Public and private addresses
Your home or office router has one public address that the internet sees. Devices behind it get private addresses from reserved ranges such as 192.168.x.x and 10.x.x.x, and the router translates between the two using NAT. That is why every computer in an office can show the same IP address on a "what is my IP" site. A third special case is 127.0.0.1, the localhost address a computer uses to talk to itself.
How a domain becomes an IP address
When someone types your web address, their device asks DNS for the matching IP. An A record holds an IPv4 address and an AAAA record holds an IPv6 one. The browser then connects to that address on the right port. Changing hosts is often just a matter of changing those records to point at the new server's address.
Example: connecting a domain to a host
A landscaping company buys a domain from one company and hosts its site with another. The host's setup page says "create an A record for @ pointing to" a specific IPv4 address. The owner adds it in the registrar's DNS records panel, and once caches update, the domain loads the new site.
When IP addresses matter for a small business
Mostly when connecting a domain, allow-listing your office for an admin panel, or excluding your own visits from analytics. IP addresses also reveal approximate location, which is how sites guess your city, but the guess is often wrong at street level and a VPN changes it entirely.
Common IP address mistakes
- Pointing DNS at a server IP that later changes. Some platforms ask for a CNAME record precisely so they can change addresses without breaking your site.
- Treating an IP as a reliable identity. Home addresses change, and many people share one public IP.
- Leaving an old AAAA record behind. Visitors on IPv6 get sent to the previous host while everyone else sees the new site.
Related terms
- DNS: the system that turns names into IP addresses.
- Domain name: the readable label that points to an IP.
- Port: picks the program at that address.
- Localhost: the special loopback address.