Fork
A split in a blockchain's history or rules, whether a brief accident or a deliberate protocol change.
A fork happens when the chain diverges into two possible paths. Sometimes it's temporary: two miners find a block at once and the network quickly drops the shorter branch. Other times it's intentional, a change to the software's rules.
Intentional forks come in two flavors. Hard forks break compatibility and can spawn a new coin; soft forks tighten rules while staying backward-compatible. Bitcoin Cash split from Bitcoin via a hard fork in 2017.
Related terms
A backward-incompatible rule change that forces every node to upgrade, sometimes splitting one chain into two.
Soft ForkA backward-compatible rule tightening where upgraded nodes enforce stricter limits and old nodes still follow along.
BlockchainA shared digital ledger that records transactions in linked batches, copied across many computers and hard to alter.
Consensus MechanismThe rules a decentralized network follows to agree on one valid history without trusting any central party.