Definition
A reorg (chain reorganization) is a consensus-level event where a blockchain’s canonical chain is replaced for a certain depth by an alternative chain with higher consensus weight, causing previously accepted blocks to be discarded and superseded. It reflects a temporary divergence and subsequent realignment of network state, affecting block ordering, transaction inclusion, and the effective confirmation status of recent data.
In Simple Terms
A reorg is when a blockchain switches from one recent version of its history to another, because the network decides a different sequence of recent blocks should be treated as the official one. Some blocks are dropped and replaced, and the transactions in those blocks are reconsidered under the new chain.
Context and Usage
The term reorg is used in discussions of consensus behavior, chain stability, and the reliability of recent confirmations on a blockchain. It appears frequently in analysis of security assumptions, finality guarantees, and the behavior of nodes and validators or miners during temporary chain splits. Reorg depth and frequency are often referenced when evaluating the robustness of a network’s canonical history.