A blockchain fork happens when the rules of a cryptocurrency network change, causing a split. This split creates a new version of the blockchain—one that shares the same history but follows new rules from that point onward. Forks can be planned (to add features or fix problems) or accidental (when blocks are mined at the same time).
There are two main types: soft forks, which are compatible with the old rules, and hard forks, which are not—often creating a new cryptocurrency. Bitcoin Cash and Ethereum Classic were both created by hard forks.
Forks can affect wallet access and recovery. For example, if you held Bitcoin before the Bitcoin Cash fork in 2017, you were entitled to Bitcoin Cash too—but only if your wallet supported the fork. Knowing how forks work helps you understand why some funds show up differently across blockchains or why recovery sometimes requires exporting private keys to claim forked coins.
