IP address
An IP address (Internet Protocol address) is a numeric identifier that points to a device or network interface on a network that uses the Internet Protocol. It makes sure data reaches the right recipient on the internet and on local networks. There are two versions of the protocol: IPv4 with 32-bit addresses and IPv6 with 128-bit addresses. The address pool is distributed by IANA through five regional internet registries. In the European Union, an IP address can be personal data.
How is an IP address built?
An IP address is a fixed-length binary number: 32 bits in IPv4 and 128 bits in IPv6. The two versions differ in notation, capacity and the year they were standardized.
| Feature | IPv4 | IPv6 |
|---|---|---|
| Address length | 32 bits | 128 bits |
| Number of addresses | 2³², about 4.3 billion | 2¹²⁸ |
| Notation | four decimal numbers 0–255 separated by dots | eight hexadecimal groups separated by colons |
| Example | 192.168.1.10 | 2001:db8::1 |
| Loopback address | 127.0.0.1 | ::1 |
| Specification | RFC 791 (1981) | RFC 8200 (2017) |
An address is split into a network part and a part that identifies the device. The boundary between them is set by the prefix, written after a slash, e.g. 192.168.1.0/24. This notation is called CIDR notation.
IPv6 was developed mainly because IPv4 addresses were running out. In IPv6 notation, leading zeros can be dropped, and one run of all-zero groups can be replaced with a double colon.
Both versions run side by side today. According to Google data reported by the Internet Society, the share of users reaching Google over IPv6 passed 50% for the first time on March 28, 2026. It stood at 50.10% that day.
What types of IP addresses are there?
IP addresses are divided by scope into public and private, and by assignment method into static and dynamic. The two divisions overlap.
| Type | Description |
|---|---|
| Public | unique across the whole internet, assigned by the service provider |
| Private | used only on a local network, not directly visible on the internet |
| Static | permanently assigned to a device or connection |
| Dynamic | assigned for a period of time, e.g. by a DHCP server, and can change |
Private IPv4 address pools are defined in RFC 1918 from 1996. They are the ranges 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. The same private addresses can be in use at once in millions of home and office networks.
Devices with private addresses connect to the internet through network address translation (NAT). The router replaces the private address with its own public address. As a result, many devices share one public address, which slowed the depletion of the IPv4 pool.
Who allocates IP addresses?
IP addresses are allocated hierarchically by IANA, which hands large blocks to regional internet registries (RIRs). The registries distribute addresses to local registries, mostly internet service providers, which pass them on to their customers.
There are five regional registries worldwide:
- AFRINIC: Africa,
- APNIC: Asia-Pacific,
- ARIN: North America,
- LACNIC: Latin America and the Caribbean,
- RIPE NCC: Europe, the Middle East and parts of Central Asia.
The IPv4 pool is gradually running out. RIPE NCC, which serves Poland among other countries, announced on November 25, 2019 that it had allocated its last /22 block. Since then it has only distributed recovered addresses, for example from companies that have closed.
Recovered addresses go to a waiting list. According to RIPE NCC, only local registries that have never received IPv4 addresses can join it. Each can get one /24 block, or 256 addresses. RIPE NCC also called for widespread IPv6 deployment.
Is an IP address personal data?
In the European Union, an IP address can be personal data, even when it is dynamic. The Court of Justice of the EU settled this in its judgment of October 19, 2016 in case C-582/14 Breyer v Germany.
The case concerned German federal websites storing users' IP addresses. The Court held that a dynamic IP address is personal data for a website operator if the operator has legal means to identify the user. This refers to information held by the internet access provider.
The judgment was based on Directive 95/46/EC, which the GDPR replaced in 2018. The Court also ruled that a website operator may have a legitimate interest in processing IP addresses, for example to protect against attacks.
Frequently asked questions
Q.What is the difference between IPv4 and IPv6?
An IPv4 address has 32 bits and is written as four decimal numbers, e.g. 192.168.1.10. An IPv6 address has 128 bits and is written in eight hexadecimal groups. IPv4 provides about 4.3 billion addresses, IPv6 provides 2¹²⁸. IPv6 was created mainly because the IPv4 pool was running out.
Q.What is the IP address 192.168.1.1?
It is an address from the private IPv4 pool 192.168.0.0/16, defined in RFC 1918. Addresses from this pool work only on local networks and are not directly visible on the internet. 192.168.1.1 is often assigned to a home router. The same address can be in use on many different networks at once.
Q.Does an IP address change?
A dynamic address can change, while a static address stays the same. A dynamic address is assigned for a set period, usually by a DHCP server at the internet provider or in the router. After that, the device may get a different address. A static address is assigned permanently, most often to servers and business connections.
Q.Can a person be identified by their IP address?
An IP address alone does not point to a person, but it can lead to one. The internet provider knows which customer it assigned the address to at a given time. That is why the Court of Justice of the EU ruled in 2016 that a dynamic IP address can be personal data. The condition is access to legal means of identifying the user.
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