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Crypto Dictionary

Hard Fork

Definition

A radical change to a network's protocol that makes previously valid blocks/transactions invalid (or vice-versa).

Deep Dive

A hard fork represents a major, backward-incompatible upgrade to a blockchain's protocol. This means that nodes running the old software version will no longer be able to validate blocks produced by nodes running the new software, and vice-versa. For a hard fork to be successful and avoid a permanent chain split, a significant majority of network participants – including miners/validators, node operators, and users – must agree to upgrade to the new rules.

Examples & Use Cases

  • 1The Ethereum Classic hard fork, which occurred after the DAO hack, splitting the Ethereum chain into ETH (rolled back transactions) and ETC (original, unrolled-back chain).
  • 2Bitcoin Cash (BCH) hard fork from Bitcoin (BTC) in 2017, driven by disagreements over block size limits and scalability solutions.
  • 3The Monero (XMR) network regularly undergoes hard forks to implement privacy enhancements and combat ASIC mining, requiring all nodes to update their software.

Related Terms

Soft ForkChain SplitBackward Incompatible

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