Fork
A change to blockchain protocol rules, either backward-compatible (soft fork) or requiring all nodes to update (hard fork).
Last Updated
2026-03-19
Related Concepts
What is Fork?
A fork occurs when a blockchain's software is updated, resulting in a change to the network's underlying rules. Depending on the nature of the change, a fork can either be a simple upgrade or a permanent split into two separate blockchains.
How does Fork work?
- Developers propose a change to the protocol's source code.
- A
Soft Forkis backward-compatible; old nodes can still validate transactions under the new rules. - A
Hard Forkis not backward-compatible; nodes must upgrade to the new software to remain part of the network. - If a significant portion of the community disagrees with a hard fork, they may continue running the old code.
- This results in the original chain splitting into two independent networks with a shared history.
Why does Fork matter?
Forks are the primary way decentralized networks evolve, fix bugs, and add new features. They are also a fundamental tool for decentralized governance, allowing a community to "exit" a project and start a new one if they are unhappy with its current direction.
Key features of Fork
- Mechanism for protocol upgrades
- Soft Fork (backward-compatible)
- Hard Fork (not backward-compatible)
- Can result in a permanent network split
- Driven by community and miner consensus
Examples of Fork
The most famous hard fork occurred in 2016 when Ethereum split into Ethereum (ETH) and Ethereum Classic (ETC) following the DAO hack. Another example is Bitcoin Cash (BCH), which split from Bitcoin (BTC) in 2017 over a disagreement about block size.