DEFINITION of Orphan Block (Cryptocurrency)

Orphan blocks are those blocks which are not accepted into the blockchain network due to a time lag in the acceptance of the block in question into the blockchain as compared to the other qualifying block. Orphan blocks are valid and verified blocks, but are rejected ones. They are also called detached blocks as they exist in isolation from the blockchain.

BREAKING DOWN Orphan Block (Cryptocurrency)

A blockchain consists of a series of blocks, which act as data storage units to store details of the various transactions occurring on the blockchain network. During the standard mining process, miners attempt to generate new blocks. The first miner who is successful in finding a new block is entitled to the block reward, and writes the first transaction for the same on the new block he/she has found. As a part of the blockchain working, the newly found block gets added as the new unit on the blockchain.

However, it is possible that two miners produce a block at a similar time. This situation occurs because the acceptance of the blocks into the blockchain by the nodes of the blockchain network does not happen instantaneously. This time lag in accepting a block may lead to another miner solving for the same exact block. It leads to a temporary mix-up on the blockchain network, as the nodes try to decide which block of the two newly identified blocks to continue with.

In such a situation, the block with the larger share of proof of work (POW) gets accepted into the blockchain. The other block, with smaller proof of work, is discarded from getting added to the blockchain and is termed as an orphan block. Such blocks are essentially valid and verified blocks, but due to network’s working mechanism and lag time leading to delayed acceptance, one of the found blocks is rejected, or orphaned.

Another way an orphaned block is created is when a hacker with sufficient hashing power attempts to reverse a few transactions that occurred earlier on the blockchain network.

Orphan blocks are most commonly linked to the popular Bitcoin cryptocurrency network. In case, if any valid transactions exist on an orphan block, they are added to the next valid block accepted on the blockchain.

Common block explorers, like Bitcoin Block Explorer, provide detailed information about the orphaned blocks, which are available online. (See also, Block Explorer.)