What is Fork?
Crypto Glossary Definition
A change in a given blockchain protocol.
Why Fork Matters
A fork is any split in a blockchain's history or rule set — it can mean a routine software upgrade (most forks) or, in rarer cases, a permanent split into two separate coins when the community can't agree on a change (as happened with Bitcoin/Bitcoin Cash and Ethereum/Ethereum Classic).
Fork in Practice
A blockchain's development team proposes a routine software upgrade to improve transaction throughput, and most node operators and miners update their software to adopt the new rules without controversy, a typical example of a fork simply meaning a change to the protocol. A separate situation looks very different: a faction of the community strongly disagrees with a proposed change, say, a plan to reverse a major hack by rewriting transaction history, while another faction insists the blockchain's history must remain immutable no matter what. Neither side backs down, and the disagreement becomes permanent. Rather than one group simply losing the argument, the blockchain splits into two separate networks that share an identical history up to the split point but diverge afterward, each maintained by nodes and miners who chose to follow one set of rules going forward. Users who held the original coin before the split now hold balances on both resulting chains, and the two assets go on to trade as entirely separate cryptocurrencies with their own prices, communities, and development teams, similar to how Ethereum split into Ethereum and Ethereum Classic. Most forks never reach this level of drama and pass as unremarkable upgrades, but the contentious kind are what most newcomers picture when they hear the word.
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