How confirmations work
A broadcast transaction first waits unconfirmed in the network's queue, the mempool. Once a miner or validator includes it in a block, the transaction has one confirmation, and the count rises by one with every block that follows.
On a proof-of-work network such as Bitcoin, finality is a matter of probability: the deeper the block, the more work an attacker would have to redo. Bitcoin's developer guide puts the average wait for one confirmation at 10 minutes and advises at least six confirmations for high-value payments, a number it calls somewhat arbitrary.
Ethereum's proof of stake adds explicit finality. Validators vote on checkpoints, the first block of each epoch of 32 slots of 12 seconds. To revert a finalised block, an attacker would have to lose at least one-third of all staked ETH.
How platforms use confirmations
Each platform sets a required count per network, and often per amount, weighing fraud risk against the customer's wait. A deposit shows as pending until the count is reached, and only then is the balance credited in the ledger and released for trading or withdrawal.
A reorganisation, where the network replaces recent blocks, can undo a transaction with few confirmations. Payment products that accept unconfirmed transfers for speed carry that risk themselves.
Confirmation, finality or card authorisation?
- Finality
- The point after which a transaction cannot be reversed. Confirmations approach it by degrees on some networks, and others declare it outright.
- Card authorisation
- An issuer's approval, which can still be reversed or charged back. A confirmed blockchain transfer has no chargeback.
Where a confirmation shows up in a platform
Modules that do the work
- Custody & walletsWallets on every major chain, with MPC custody from leading providers or your own keys.
- LedgerThe double-entry book of record behind every balance, fee and transfer.
- NotificationsEmail, SMS, push and in-app messages in your brand, through the providers you choose.
Platforms that need it
Where it is written
The laws and standards this page's facts come from.
- Bitcoin Developer Guide, Payment processing: confirmations (developer.bitcoin.org)
- Ethereum.org, Proof-of-stake (developer documentation)
General information, not legal advice: what applies to you depends on your services and your market.