Chain Reorganization

Chain reorganization, or "reorg," is a process in blockchain where the network discards the current chain of blocks and replaces it with a longer chain. This can occur when two miners find a solution to the cryptographic puzzle at the same time, creating two competing chains. The chain with the most work or the longest chain is accepted by the network, and the blocks from the discarded chain are returned to the mempool, awaiting confirmation in the new chain. While chain reorganizations are normal occurrences in the functioning of blockchain, deep reorgs involving multiple blocks are rare and can be problematic, as they may result from malicious actions like a 51% attack, leading to double-spending or network instability.