What is a hard fork

A hard fork is a permanent split in a blockchain's rules that makes new blocks incompatible with old software, forcing every node to upgrade or get left behind. It matters because forks can create entirely new coins, change core economics, or fix bugs, and holders sometimes wake up owning assets on two separate chains. Bitcoin's 2017 split into Bitcoin (BTC) and Bitcoin Cash (BCH) happened because developers disagreed over block size limits; anyone holding BTC before the fork ended up with equal BCH too. The natural next question is whether a hard fork is risky: it can be, since it splits the network's security and community, and old nodes that don't upgrade get stuck on an abandoned chain. Not every fork creates a new coin though; some, like Ethereum's regular protocol upgrades, are backed by near-universal consensus and cause no split at all.