What is an IP address?

An IP address (Internet Protocol address) is a unique numeric identifier assigned to every device connected to a computer network using the Internet Protocol. It serves two primary purposes: host identification and location addressing, allowing data packets to be routed between devices across the Internet.

The most common IP address format today is IPv4, which uses 32-bit addresses written as four decimal numbers separated by dots (e.g. 192.0.2.42). Each number ranges from 0 to 255. This gives a total of about 4.3 billion possible addresses.

IPv4 addresses are assigned hierarchically: Regional Internet Registries (RIRs) receive large blocks from IANA, then allocate smaller blocks to ISPs and organizations. When you visit a website, your device's IP is in the packet's source field, and the server's IP is in the destination field — routers in between use these to forward the packet along.

Related terms: CIDR block, ASN, subnet mask, IPv6.