A hard fork is an irreversible protocol upgrade that splits a blockchain into two separate chains with different rules. When a hard fork occurs, network nodes must upgrade to the new protocol—those that don't will reject the new blocks, creating a split into two independent chains.
Hard forks happen to upgrade protocol features, fix security vulnerabilities, or resolve community disagreements. The most prominent example is the August 2017 Bitcoin hard fork that created Bitcoin Cash, triggered by disagreement over block size limits.
When a hard fork occurs, you typically receive equivalent coins on both chains. If you held 1 Bitcoin before the fork, you'd now hold 1 Bitcoin and 1 Bitcoin Cash. This duplication creates both opportunity and risk.
For traders, hard forks cause significant market volatility. The community and markets must decide which chain will retain value and support. Before a fork, speculative positioning often drives sharp price moves. After a fork, if both chains persist, you hold assets on two networks—but the combined value may not equal the pre-fork price. The key is monitoring which chain attracts developer support and exchange listings, as this determines long-term viability and liquidity.
