Hard fork

A hard fork is a permanent change to a blockchain protocol that results in the network splitting into two separate chains, each with its own transaction history and rules. This update is not backward-compatible, meaning nodes running the old version of the software cannot interact with those on the new version. Hard forks can be planned (for network upgrades) or arise due to community disagreements over the project’s direction.

Notable examples of hard forks include the 2017 split of Bitcoin into Bitcoin Cash (BCH), caused by disputes over network scaling, and the 2016 split of Ethereum into Ethereum and Ethereum Classic (ETC) following the DAO hack. Hard forks can lead to the creation of new cryptocurrencies and often spark controversy, but they are also a crucial tool for implementing major blockchain improvements.