A chain reorganisation replaces one or more recent blocks with a competing set, and any transaction that was in a replaced block goes back into the unconfirmed queue as if it had never been mined. For a withdrawal that had one confirmation and now has none, the effect is a delay of one block, after which it is mined again. For a withdrawal already past the casino’s confirmation threshold, a reorganisation deep enough to reach it is so rare on the main chains that sites size their thresholds to make it practically impossible. The coins are not lost in either case. They are either re-mined or still on the casino ledger.
Reorganisations of one block happen on Bitcoin a few times a month and on faster chains more often, which is why most crypto roulette sites wait for several confirmations before treating a deposit as final and why a withdrawal can show a confirmation count that briefly goes down.
Why blocks get replaced
Two miners sometimes find a valid block at almost the same moment. Part of the network builds on one, part on the other, and the chain has two tips for a few seconds. Whichever tip gets the next block becomes the main chain, and the other block is orphaned. Any transaction in the orphaned block that is not also in the winning one drops back to the queue. Almost always, the same transactions are in both because both miners drew from the same queue, so the effect is a confirmation count that dips by one and recovers within ten minutes.
What you see on a withdrawal
The casino signs and broadcasts the withdrawal. The explorer shows it in a block with one confirmation. Then a competing block wins, and the explorer shows the transaction as unconfirmed again, or as included in a different block at the same height. Within a block or two, it is confirmed on the winning chain, and the count climbs as before. Nothing needs to be done, and the casino does not need to resend, because the transaction was never invalid, only not yet settled.
Why confirmation thresholds exist
A deeper reorganisation, replacing three or six blocks, would be needed to reverse a transaction the casino had already treated as final, and the cost of producing that many blocks faster than the rest of the network puts it out of reach on Bitcoin and Ethereum. Ethereum goes further and finalises blocks after about fifteen minutes, past which no reorganisation is possible. Solana and Tron have similar finality after seconds or a minute. Sites set their deposit thresholds at the depth where reversal becomes impractical for each coin, which is why the numbers differ from coin to coin.
Typical depth of reorganisations seen in practice, and the threshold sites used against them:
- Bitcoin – One-block reorganisations occur, two-block ones are rare, and anything deeper has not happened for years. Sites wait one to six blocks.
- Litecoin and Dogecoin – One-block reorganisations are more frequent because blocks are faster. Sites wait three to six.
- Ethereum – Short reorganisations of one or two blocks happen, and finality after around fifteen minutes ends the question. Sites wait twelve blocks or for finality.
- Smaller proof-of-work coins – Attackers have forced deeper reorganisations on some. Sites wait longer, pause the coin, or remove it.
A pending withdrawal caught in a reorganisation is delayed by a block. The threshold that made you wait on the deposit is the same thing that keeps the withdrawal safe once it clears.
