Reorg

Definition ∞ A reorg, or reorganization, on a blockchain refers to a situation where two or more valid chains of blocks exist simultaneously, and one is ultimately discarded in favor of another. This typically occurs in proof-of-work systems when multiple miners find a valid block at roughly the same time. The network eventually converges on a single chain, invalidating the blocks on the shorter or less-favored chain. Reorgs can impact transaction finality and are a normal, though sometimes concerning, aspect of certain blockchain consensus mechanisms.
Context ∞ Discussions surrounding reorgs often highlight their potential to cause transaction double-spending or introduce uncertainty regarding the finality of past transactions. Developers continuously work to minimize the frequency and depth of reorgs through protocol adjustments and consensus rule refinements. The context for understanding reorgs is critical when assessing the security and reliability of blockchains, particularly for financial applications where transaction finality is paramount. Future improvements aim to enhance the predictability and immutability of the ledger.