Uncle Block
ethereum · consensus
A valid proof-of-work Ethereum block that was not canonical but could still be referenced for partial rewards.
- Also known as
- Ommer Block, Orphan (Ethereum context)
An uncle, later called an ommer, was a valid Ethereum proof-of-work block mined near the same time as the canonical block but not selected for the main chain. Ethereum rewarded referenced ommers to reduce miner variance and reflect network work.
Uncle blocks were relevant before Ethereum's transition to proof of stake. Other chains may use "orphan" or "stale" for similar competing blocks, but reward rules differ by protocol.
Related terms
Block
→A batch of valid transactions added to a blockchain, linked to the previous block by a cryptographic hash.
mining · blockchain · security
Chain Reorganization
→A network event where the active chain tip switches to a different branch with more accumulated work.
blockchain · security
Confirmations
→The count of blocks confirming a transaction, usually including the block that first contains it.
security · blockchain