GlossaryIntermediate
Hard Fork
A protocol change that is not compatible with older versions of the software.
A hard fork is a change to a blockchain's rules that isn't backward-compatible, meaning nodes running the old software will reject blocks produced under the new rules, and vice versa.
If not every participant upgrades, a hard fork can split a network into two separate chains that share the same history up to the fork point but diverge afterward. See Kaavon's "Soft Fork" glossary definition for a backward-compatible alternative that doesn't carry this same split risk.
Examples
- A hard fork might be used to add a new feature that changes how blocks are validated.
- Some well-known cryptocurrencies exist today because of a hard fork that split an earlier network into two.