Orphan Block

A block without ancestry on a blockchain network, one that has been discarded.

An orphan block is a special kind of block on blockchain networks because they don’t seem to belong. Such a block may either contain no historical information, meaning that it has no parent block in the form of a connection to a block that was mined before it or has been discarded because of a similarly mined block. In both cases, an orphan block has no active use on the blockchain because it is irrelevant.

Orphan blocks are not possible currently, although they used to exist. However, these blocks occur from time to time when two blocks with the same information are broadcast to nodes at the same time. One is eventually validated and added to the network, while the other is discarded, making it an orphan block.