Glossary
Reorg (Chain Reorganization)
An event where a node discards a chain tip in favor of a different one with more work or stake — the canonical history changes, recent transactions may revert.
A reorg happens when a node receives a chain tip with more work (PoW) or more attested stake (PoS) than the one it was building on, and switches to follow the new tip. Transactions that were in the abandoned blocks but not in the new ones effectively un-happen and re-enter the mempool.
Single-block reorgs are normal in PoW and uncommon but seen in PoS. Deeper reorgs are rare and typically signal either a network split or a successful attack. The 7-block reorg on Ethereum in May 2022 prompted significant client-software hardening.