An IP address is a numeric label that identifies a device's network interface on a network using the Internet Protocol, so that data can be delivered to the right place. Think of it as the return address on every packet your phone, laptop or server sends.
The short answer
IP stands for Internet Protocol, the set of rules that decides how data is split into packets, addressed and moved between networks. Every packet carries two IP addresses: a source (where it came from) and a destination (where it is going). Routers along the way read the destination address and forward the packet one hop closer to its target, much like sorting offices reading the postcode on a letter.
Without IP addresses, the internet would have no way to tell your request for a web page apart from anyone else's, or to send the reply back to you. You can see the public IP address your connection is using right now on the ToolsForAnyone home page.
What an IP address looks like
There are two versions of the Internet Protocol in use today, and their addresses look quite different.
IPv4 addresses
An IPv4 address is a 32-bit number, normally written as four decimal numbers between 0 and 255 separated by dots, for example 203.0.113.42. Each of the four parts is called an octet because it represents 8 bits. Because the address is 32 bits long, there are 232 possible IPv4 addresses, which is about 4.3 billion. That sounded like plenty in the early 1980s, but it is far fewer than the number of connected devices in the world today.
IPv6 addresses
IPv6 was designed to solve that shortage. Its addresses are 128 bits long and written as eight groups of four hexadecimal digits separated by colons, such as 2001:0db8:0000:0000:0000:ff00:0042:8329. Leading zeros in a group can be dropped and one run of all-zero groups can be replaced with ::, so the same address can be shortened to 2001:db8::ff00:42:8329. There are 2128 possible IPv6 addresses, roughly 3.4 × 1038, which is effectively inexhaustible.
Our guide to IPv4 vs IPv6 covers the differences in depth, and the IP address converter lets you see the same address in decimal, binary and hexadecimal form.
203.0.113.0/24 and 2001:db8::/32 used in examples on this page are reserved for documentation. They never appear on the real internet, which makes them safe to use in tutorials.How IP addresses work
When you type a website name into your browser, several things happen in quick succession:
- Your device asks a DNS resolver to translate the name (for example
example.com) into an IP address. This is explained in What Is DNS and How Does It Work? - Your device builds packets addressed to that IP, with its own address as the source.
- The packets go to your router, which forwards them to your internet service provider (ISP).
- Routers across the internet use routing tables, built largely with the Border Gateway Protocol (BGP), to pass each packet toward the network that owns the destination address.
- The web server replies to the source address, and the process runs in reverse.
IP itself is a "best effort" protocol: it does not guarantee that packets arrive, or arrive in order. Higher-level protocols such as TCP handle retransmission and ordering, while UDP leaves that to the application. IP's job is purely addressing and routing.
Network and host parts
Every IP address is split into a network portion and a host portion. The network portion identifies which network the device belongs to; the host portion identifies the specific device within it. The split is described by a prefix length or subnet mask, such as 192.168.1.0/24 or 255.255.255.0. Routers on the internet only need to know how to reach the network, not every individual device. If you want to work through the maths, see Subnet Masks and CIDR Notation Made Simple.
Types of IP addresses
IP addresses are usually described along two independent axes: where they are reachable from, and how they are assigned.
Public vs private
A public IP address is globally unique and reachable on the internet. Your ISP assigns one to your router. A private IP address comes from ranges reserved for internal networks (such as 192.168.0.0/16 and 10.0.0.0/8) and is only meaningful inside your home or office. Your router uses Network Address Translation (NAT) so that many private devices can share one public IPv4 address. Read more in Public vs Private IP Addresses Explained.
Static vs dynamic
A dynamic address is handed out automatically, usually by DHCP, and may change over time. A static address is fixed and does not change unless someone reconfigures it. Most home connections use dynamic public addresses, while servers and many business connections use static ones. See Static vs Dynamic IP Address for the trade-offs.
Special-purpose addresses
| Address or range | Purpose |
|---|---|
127.0.0.1 and ::1 | Loopback ("localhost"): the device talking to itself |
169.254.0.0/16 and fe80::/10 | Link-local: self-assigned when no other address is available |
100.64.0.0/10 | Shared address space for carrier-grade NAT used by some ISPs |
224.0.0.0/4 and ff00::/8 | Multicast: one sender, many receivers |
0.0.0.0 | "This host" or "any address", depending on context |
Who assigns IP addresses?
IP addresses are allocated in a hierarchy. The Internet Assigned Numbers Authority (IANA) manages the global pool and delegates large blocks to five Regional Internet Registries (RIRs): ARIN (North America), RIPE NCC (Europe, the Middle East and parts of Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America and the Caribbean) and AFRINIC (Africa). The RIRs allocate smaller blocks to ISPs, hosting companies and large organisations, which in turn assign individual addresses to customers and devices.
Registration records for these blocks are public. A WHOIS lookup on an IP address shows which organisation holds the block, and the block's routing is announced by an Autonomous System, identified by an ASN.
What your IP address reveals about you
Your public IP address is visible to every website and online service you connect to; it has to be, or they could not reply. On its own, it typically reveals:
- Your ISP or network operator, and its ASN.
- An approximate location, usually accurate to the country and often to the region or city, but rarely to a street address.
- The type of connection in some cases, such as mobile, residential, business, hosting provider or VPN.
It does not reveal your name, email address or exact home address to an ordinary website. Your ISP knows which customer was assigned an address at a given time, and that record can be disclosed in response to legal process, but it is not published. Geolocation databases are often wrong, sometimes by hundreds of kilometres; see How Accurate Is IP Geolocation? to understand why.
You can check what any address reveals with the IP lookup tool.
Should you hide your IP address?
For most people, a visible IP address is not a serious risk. Sensible precautions are to keep your router's firmware updated, avoid exposing unnecessary ports to the internet, and be cautious about sharing your IP in public forums or games where someone might try to flood your connection. If you want more privacy, a VPN, Tor or a feature like iCloud Private Relay will show websites a different address. Our guide on how to hide your IP address compares the options.
Frequently asked questions
Does every device have its own IP address?
Every network interface that talks IP has at least one address, so your phone, laptop and smart TV each have their own private address on your home network. On the internet side, however, they usually share your router's single public IPv4 address. With IPv6, each device commonly gets its own globally routable address.
Can two devices have the same IP address?
Two devices on the same network cannot share an address without causing a conflict. Devices on different private networks can, and routinely do, use the same private address, such as 192.168.1.10, because private addresses are never routed on the public internet.
Is my IP address the same as my MAC address?
No. A MAC address is a hardware identifier used only on the local network segment (for example, between your laptop and your Wi-Fi router). An IP address is a logical address used to route traffic across networks. Your MAC address is not visible to websites you visit.
Why does my IP address change?
Most ISPs assign dynamic addresses through DHCP. Your address can change when the lease expires, when your router restarts, or when the ISP reorganises its network. Mobile networks change addresses even more often.
How do I find my IP address?
Your public IP is shown on the ToolsForAnyone home page. To find your local (private) address on a specific device, follow the steps in How to Find Your IP Address on Any Device.