In blockchain technology, a hard fork occurs when there is a radical change to the protocol that makes previously invalid blocks/transactions valid (or vice-versa). This often leads to the creation of a new version of the blockchain and can create two different cryptocurrencies. For example, Bitcoin and Bitcoin Cash are the results of a hard fork from the original Bitcoin blockchain. Hard forks can be contentious and usually occur when there is disagreement among stakeholders regarding the future direction of the network.