What is Uncle / Ommer Block?
An uncle (or ommer) block is a valid block produced near the same time as another block but not included in the canonical chain. Pre-Merge Ethereum rewarded uncles to compensate miners for orphaned work and improve security with fast block times.
Why Uncle / Ommer Block matters
Understanding Uncle / Ommer Block is part of building a solid mental model of how Bitcoin, blockchain and Web3 systems actually work. Concepts in the Concepts category sit at the foundation of the broader stack — get them right and the rest is far easier.
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Related terms
- Block — A bundle of transactions added to the blockchain.
- Reorganization (Reorg) — Replacing recent blocks with a competing chain that has more work.
- Ethereum — A programmable blockchain that supports smart contracts.
More concepts terms
- Decentralization — Distributing control across many independent participants.
- Atomic Swap — Trustless cross-chain trade using hash time-locked contracts.
- Bridge — A protocol that moves assets or messages between chains.
- Byzantine Fault Tolerance (BFT) — A system that works even when some nodes lie or fail.
- Staking — Locking tokens to secure a network and earn rewards.
- Validator — A node that proposes and attests to blocks in PoS.
- Layer 1 (L1) — A base blockchain network with its own consensus.
- Layer 2 (L2) — A scaling network that settles to a Layer 1.
Keep exploring
Continue with the full blockchain glossary — 136 terms in total — or read the developer blog and FAQ for deeper context.