A hard fork is a type of upgrade or modification to a blockchain protocol where the existing blockchain splits into two separate chains. This occurs when the consensus rules of the blockchain are changed, and nodes that do not update to the new rules are considered invalid by the upgraded network. As a result, a hard fork leads to a divergence in the blockchain, creating two distinct chains with separate transaction histories and potentially separate cryptocurrencies. Hard forks can be planned and implemented by the blockchain development team or can occur due to disagreements within the community and result in a split a**** users and miners.
During a hard fork, the new chain and its associated rules and protocols are incompatible with the old chain. This means that any transactions, balances, and smart contracts on the old chain are not recognized by the new chain, and vice versa.
Hard forks can occur for various reasons, such as adding new features, improving security, addressing scalability issues, or resolving disagreements within the community on how the blockchain should be governed or operated. Examples of hard forks in the cryptocurrency space include the Bitcoin Cash fork from Bitcoin, or the Ethereum Classic fork from Ethereum.
It is important to note that a hard fork can create divided communities, as some members may choose to stick with the old chain while others migrate to the new chain.