A fork is an event in which a blockchain protocol changes its underlying software rules, altering how network nodes validate transactions and potentially splitting the chain into two paths.
How Blockchain Forks Operate
Distributed ledgers rely on software clients running matching consensus rules to agree on transaction histories. When developers change these validation parameters, network nodes must choose whether to adopt the new rules. The technical implementation determines how the network handles this transition:
- Hard Forks: A non-backward-compatible update where non-upgraded nodes reject blocks produced under the new rules. If part of the mining or validator community continues running legacy software, the ledger permanently branches into two distinct, parallel blockchains with shared history prior to the split point.
- Soft Forks: A backward-compatible update where new rules restrict or tighten existing validation logic. Nodes running older software still recognize blocks created by upgraded nodes as valid, allowing the network to maintain a single continuous chain as long as a majority of mining power or validator stake enforces the upgrade.
- Temporary Accidental Forks: Occur naturally when two miners find valid blocks almost simultaneously. Nodes resolve this divergence automatically by following the cumulative proof-of-work or longest-chain rule once the subsequent block is mined.
Network Upgrades Versus Codebase Forks
A network fork specifically alters live consensus state or validation logic across active distributed nodes. In contrast, a codebase software fork simply copies and modifies open-source repository code to launch an entirely separate network from a new genesis block, without sharing existing transactional ledger history.