Transactions don’t start out as irreversible. Instead, they get a confirmation score that indicates how hard it is to reverse them (see table). Each confirmation takes between a few seconds and 90 minutes, with 10 minutes being the average. If the transaction pays too low a fee or is otherwise atypical, getting the first confirmation can take much longer.
|Confirmations||Lightweight wallets||Bitcoin Core|
|0||Only safe if you trust the person paying you|
|1||Somewhat reliable||Mostly reliable|
|6||Minimum recommendation for high-value bitcoin transfers|
|30||Recommendation during emergencies to allow human intervention|