What Is a Hard Fork (Blockchain)?
A hard fork is a permanent divergence from the previous version of a blockchain network. It occurs when non-upgraded nodes can no longer validate blocks created by upgraded nodes that follow newer consensus rules. This essentially creates two separate blockchains going forward with their own set of rules and protocols, which are incompatible with each other.
Hard forks are used to upgrade or change the existing protocol in order to add new features or fix security issues. They also allow for changes such as increasing the size of blocks on a blockchain, changing transaction speeds, and altering how miners receive rewards for validating transactions. Hard forks can be contentious if there is disagreement among stakeholders about whether they should occur or not; this has been seen in Bitcoin’s history where some users have disagreed over proposed upgrades leading to multiple versions of Bitcoin being created (e.g., Bitcoin Cash).