Glossary

Fork

Plain-language definition Crypto glossary

Key takeaways

A fork is a divergence in a blockchain's rules or history that happens when participants adopt different versions of the protocol, splitting the single agreed path into two.
A soft fork tightens the rules in a backward-compatible way so non-upgraded nodes still accept new blocks, while a hard fork changes the rules incompatibly and can permanently split the chain into two networks.
Forks are how decentralized networks upgrade and resolve disagreements, and a contentious hard fork can create an entirely new cryptocurrency while routine soft forks let a network improve smoothly.

Definition

A fork is a divergence in a blockchain’s rules or history. It happens when participants adopt different versions of the protocol, splitting the single agreed path into two.

How it works

A soft fork tightens the rules in a backward-compatible way, so nodes that do not upgrade still accept the new blocks. A hard fork changes the rules in a way that is not backward-compatible; if part of the community keeps running the old rules, the chain permanently splits into two networks, each with its own coin and history from the split point onward.

Why it matters

Forks are how decentralized networks upgrade and how disagreements get resolved when consensus breaks down. A contentious hard fork can create an entirely new cryptocurrency and divide a community, while routine soft forks let a network improve smoothly.

Example

Bitcoin Cash split from Bitcoin through a hard fork over how to scale the network.

FAQ

Frequently asked questions

What is the difference between a soft fork and a hard fork?

A soft fork tightens the rules in a backward-compatible way, so nodes that do not upgrade still accept the new blocks. A hard fork changes the rules in a way that is not backward-compatible, and if part of the community keeps the old rules, the chain permanently splits into two separate networks.

Can a fork create a new cryptocurrency?

Yes. A contentious hard fork can split a network into two, each with its own coin and its own history from the split point onward. Bitcoin Cash, for example, split from Bitcoin through a hard fork over how to scale the network.

Why do forks happen?

Forks are how decentralized networks upgrade their software and how disagreements get resolved when consensus breaks down. Routine soft forks let a network improve smoothly, while a contentious hard fork can divide a community into two chains.