What Is a Fork? Hard vs Soft Forks

When a community disagrees on rules or upgrades, a chain can "fork." Understanding forks explains coins like BCH and ETC.

Soft Fork vs Hard Fork

A soft fork is a backward-compatible tightening of rules; old nodes still accept new blocks and the network stays unified. A hard fork is an incompatible rule change; un-upgraded nodes reject the new blocks — and if both sides persist, the chain splits in two, creating a new coin.

Historical Examples

Bitcoin Cash (BCH) hard-forked from Bitcoin over a block-size dispute; Ethereum Classic (ETC) is the original chain left after Ethereum forked following The DAO hack. Holders of the original coin usually receive an equal amount of the new coin — but beware phishing that abuses "fork airdrops."