What is Hard Fork?
A hard fork is a protocol change that loosens or alters consensus rules so that new blocks are rejected by old nodes. If both sides keep running, the chain permanently splits — as happened with Bitcoin Cash forking from Bitcoin in 2017.
Why Hard Fork matters
Understanding Hard Fork is part of building a solid mental model of how Bitcoin, blockchain and Web3 systems actually work. Concepts in the Concepts category sit at the foundation of the broader stack — get them right and the rest is far easier.
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Reading the definition is a start. ZeroToBlock teaches concepts like Hard Fork through hands-on, browser-based simulations. Build the mental model by actually using it:
- Bitcoin 101 — interactive fundamentals course
- Bitcoin Proof of Work — mining, hashing and consensus
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Related terms
- Soft Fork — A backwards-compatible protocol upgrade.
- Fork — A divergence in the blockchain or its rules.
- Reorganization (Reorg) — Replacing recent blocks with a competing chain that has more work.
More concepts terms
- Decentralization — Distributing control across many independent participants.
- Atomic Swap — Trustless cross-chain trade using hash time-locked contracts.
- Bridge — A protocol that moves assets or messages between chains.
- Byzantine Fault Tolerance (BFT) — A system that works even when some nodes lie or fail.
- Staking — Locking tokens to secure a network and earn rewards.
- Validator — A node that proposes and attests to blocks in PoS.
- Layer 1 (L1) — A base blockchain network with its own consensus.
- Layer 2 (L2) — A scaling network that settles to a Layer 1.
Keep exploring
Continue with the full blockchain glossary — 136 terms in total — or read the developer blog and FAQ for deeper context.