Definition
A hard fork is a protocol change that is not fully backward-compatible with the previous validation rules. To follow blocks relying on the changed rules, participating software generally needs to adopt the update. The term describes compatibility; it does not automatically mean an argument, a security incident or a new tradeable coin.
How It Works
A coordinated network upgrade can activate new behavior at a specified condition, such as a block height or timestamp. If participants broadly move to the new rules, the old branch may not continue as an active network. If different groups keep supporting incompatible rules, separate chains can persist with a shared earlier history.
Key Considerations
Before an upgrade, operators should understand which software and rules their chosen network requires. Custodial services may pause transfers while handling the transition. Where separate chains persist, replay protection and chain identifiers can affect transaction safety. An old node may remain connected yet reject newly permitted blocks. The existence of a fork does not establish which branch is more secure, valuable or appropriate for a user’s needs.