Hard Fork
A hard fork is a change to a blockchain’s protocol that is so deep it is incompatible with previous versions of the software. Nodes that do not update to the new rules can no longer validate the blocks produced under the new protocol.
When part of the community adopts the new rules and another part keeps the previous ones, a hard fork can give rise to two distinct blockchains, each with its own crypto-asset. A hard fork is distinct from a soft fork, which is instead backwards-compatible.
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