Overview
A hard fork is a backward-incompatible chain split that creates two separate networks with different rules. Nodes that do not upgrade are excluded. Hard forks can be planned upgrades or community splits.
How It Works
A protocol change makes new blocks invalid to old nodes, forcing a split. Users and applications choose which chain to follow. This can create new tokens, as with Bitcoin Cash and Ethereum Classic.
Why It Matters
Hard forks enable major upgrades but can fragment communities and assets. They require coordination and clear communication. They are a defining feature of permissionless networks.
Related Concepts
Hard Forks relate to Soft Forks, Consensus, and Chain splits. They are a mechanism for Protocol upgrades.