Glossary

Hard Fork

1 min read

A fork generally is a change to a project’s source code. Bitcoin is an open-sourced project, meaning that anyone can access, download, or alter the source code without permission.

A hard fork specifically is a consensus change that is not backwards compatible. Backwards incompatibility occurs when a previously invalid behavior is made valid. In order to maintain consensus across a hard fork, all nodes are required to upgrade. Otherwise, old nodes will reject transactions or blocks as invalid under the old rules, while upgraded nodes will accept them as valid. For this reason, hard forks are avoided at all costs in Bitcoin.

Related Terms
Fork
A fork is a change to a protocol or a piece of code. There are two types of forks: soft forks and hard forks.
Learn more.
Soft Fork
A soft fork is a fork, or a change to a project's source code, which is backwards compatible, meaning that it is not imperative that all nodes adopt the upgrade.
Learn more.
Consensus
Consensus is the ideal and the method of coordination between individuals in a decentralized system. Consensus is achieved at the development level with regards to changes to the Bitcoin protocol, and it is also achieved with regards to agreement on the state of the blockchain.
Learn more.
Bitcoin Node
A node is a discrete member of a network which interacts with other nodes to form the network. Bitcoin nodes store and validate the blockchain and exchange blocks and transactions with one another in order to maintain consensus.
Learn more.
Explore More Terms →