Orphan Block

An orphan block is a block that is successfully mined but not included in the main blockchain. Orphan blocks occur due to the decentralized nature of mining, where multiple miners may solve the proof-of-work puzzle at nearly the same time. When this happens, both blocks are broadcast to the network, but only one can be added to the blockchain. The network typically chooses the block that is part of the longest chain, based on the blockchain’s consensus rules. The other block, though valid, becomes an orphan block and is discarded from the main chain.

The phenomenon of orphan blocks highlights the competitive and probabilistic nature of mining in decentralized networks like Bitcoin. When two miners solve a block simultaneously, the network must eventually converge on a single chain to maintain a consistent ledger. This process is resolved as more blocks are mined: the chain that receives the next valid block first becomes the longest chain, and the network discards the shorter chain, turning its blocks into orphan blocks. The transactions in an orphan block are not lost but are typically reprocessed and included in subsequent blocks.