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Fork

In IcelandicKvíslun

A change to a blockchain's rules; if not every node follows the change, the chain can split into two separate chains, each with its own coin.

A fork is when the rules of a BlockchainBlockchainA public ledger where transactions are grouped into blocks, each linked to the one before, so past records can't be altered without it showing. change, or when the chain splits into two branches. Picture a road that divides in two: from a certain BlockBlockA batch of transactions added to a blockchain in one go, together with a reference to the block before it. onwards, there are two paths. Everything recorded before the split is shared by both branches.

Soft forks and hard forks

  • A soft fork tightens the rules in a way that older software still accepts the new blocks. Nodes that don't upgrade can stay on the same chain. Bitcoin's SegWit upgrade, which took effect on 24 August 2017, was a soft fork.
  • A hard fork changes the rules so that older software rejects the new blocks. If everyone upgrades, the network carries on as a single chain. If some nodesNodeA computer that runs a crypto network's software, keeps a copy of the blockchain and checks that new transactions and blocks follow the rules. refuse to upgrade, two chains and two coins emerge.

Examples of splits

  • Ethereum Classic. After an attack on a smart contract called The DAO, Ethereum's rules were changed on 20 July 2016 to recover the funds. Part of the community rejected the change and kept the old chain running under the name Ethereum Classic.
  • Bitcoin Cash. A dispute over block size led Bitcoin Cash to split from BitcoinBitcoinThe first and largest cryptocurrency: a digital currency that no single party controls, with a fixed limit of 21 million coins. on 1 August 2017.

In both cases, anyone who held coins before the split received the same amount of the new coin.

What to keep in mind

The word is also used when developers take open-sourceOpen sourceSoftware whose source code is open to everyone, so anyone may read it, use it, change it and share it. software and start a new project from its code. Many cryptocurrencies began this way, from Bitcoin's code.

Everything in Myntkaup Learn is written and regularly reviewed by the Myntkaup editorial team. It is for education and is not investment advice. Editorial policy. Updated 18 October 2026.