Definition
Reorg protection refers to the practices that guard a recipient against a chain reorganization quietly undoing a transaction they believed was settled. A reorganization, or reorg, happens when the network temporarily adopts a different branch of the blockchain as the canonical one, discarding blocks that were briefly considered valid. Transactions only in the discarded blocks return to the mempool and may not reappear in the new chain.
How reorgs occur
Most reorgs are benign and shallow. When two miners find blocks at nearly the same time, the network briefly splits until one branch gains the next block and becomes the longest, settling the tie. Single-block reorgs happen periodically as a normal part of operation. Deeper reorgs are far rarer and would require either extraordinary luck or a large amount of adversarial hashpower attempting to rewrite recent history.
Protecting yourself
The primary defense is depth: the more confirmations a transaction has, the more proof-of-work a reorg would need to discard, making reversal exponentially less likely. Recipients scale their required confirmations to the value at risk and may raise the threshold during episodes of mining-power concentration or network instability. Because a discarded transaction returns to the mempool rather than vanishing, funds are not destroyed, but a payment can become un-received, which is precisely the outcome confirmation thresholds are meant to prevent.
See confirmations depth and probabilistic finality for the underlying mechanics.
In Simple Terms
Reorg protection refers to the practices that guard a recipient against a chain reorganization quietly undoing a transaction they believed was settled. A reorganization, or…