Hard Fork

A hard fork is a change to a blockchain’s protocol rules that older software does not recognize as valid. Because blockchains rely on many independent computers agreeing on the same rules, a non-backward-compatible update can divide the network: upgraded nodes follow the new rules, while non-upgraded nodes may continue following the old ones. If both sides keep producing blocks, the result can be two separate chains with a shared history up to the fork point.

Hard forks matter because they are a way to make major upgrades, fix serious issues, change governance or economics, or intentionally create a new blockchain community. They require coordination among developers, node operators, miners or validators, exchanges, and users. A practical example is Bitcoin Cash, which split from Bitcoin after disagreement over block size rules. By comparison, a soft fork tightens or adds rules in a way that older nodes can still accept, while a hard fork requires everyone who wants to stay on the same chain to upgrade.