IPv4 (Internet Protocol version 4) is the set of rules that identifies every device connected to the internet or a local network using a unique numerical address. An IPv4 address looks like this: 192.168.1.1. It consists of four groups of numbers (called octets) separated by full stops, where each number ranges from 0 to 255.
IPv4 has been the backbone of internet communication since the 1980s. It works by breaking data into small packets, labelling each one with a sender's address and a recipient's address, then routing those packets across networks until they reach their destination. Your router, laptop, smartphone, and smart TV all use IPv4 addresses to talk to each other and to the wider internet.
The main limitation of IPv4 is that it can only create about 4.3 billion unique addresses. As the number of internet-connected devices exploded in recent decades, the pool of available IPv4 addresses became scarce. This scarcity has driven the slow adoption of IPv6, which allows for vastly more addresses. However, IPv4 remains dominant because replacing it across the entire internet would require massive infrastructure changes.
When buying broadband or setting up a home network, your internet service provider assigns your router a public IPv4 address (the one visible to the wider internet). Inside your home, your router typically assigns private IPv4 addresses to your devices (usually starting with 192.168 or 10.0). If you run servers, host a website, or need a fixed address for remote access, check whether your broadband deal includes a static IPv4 address rather than one that changes periodically.