Orphan Block

What is Orphan Block?

An orphan block is a valid block that was successfully mined but rejected by the network when two miners solve a block simultaneously, forcing the network to choose one chain and abandon the other.

How does Orphan Block work?

1. Two miners solve the next block at roughly the same time.
2. Both broadcast their valid blocks different nodes receive them in different orders.
3. A temporary fork forms as part of the network follows each block.
4. When the next block is mined on top of one branch, that chain becomes longest.
5. Nodes on the shorter branch discard their block it becomes an orphan.

Why does Orphan Block matter?

The miner of the orphaned block earns no reward despite valid work. Orphan blocks also cause brief delays in transaction finality.

Key features of Orphan Block

• Valid block not included in the canonical chain
• Result of simultaneous mining and network latency
• Resolved automatically by the longest-chain rule
• Transactions in orphans must be re-included in future blocks

Examples of Orphan Block

Early Bitcoin saw orphan blocks every few days. Ethereum called these "uncle blocks" and paid partial rewards to miners.

Faster block times (like Litecoin) produce more orphans than slower ones.