Confirmation

Confirmation is the process by which a network keeps proving, block after block, that a transaction really belongs in the permanent record. The first confirmation happens the moment a transaction is packed into a block that miners or validators accept; every additional block mined or finalized on top of it adds one more confirmation, each one making the transaction harder to reverse.

On proof-of-work chains like Bitcoin, confirmations are probabilistic: rewriting history would mean out-racing the entire honest network with more computing power, which becomes exponentially less likely with each added block. The old rule of thumb was six confirmations (roughly an hour at Bitcoin's ten-minute block time) before treating a payment as final, a figure chosen to make a 51% attack statistically negligible. In practice most exchanges now settle deposits after just one to three confirmations for everyday amounts, reserving stricter thresholds for large transfers.

Proof-of-stake networks handle this differently. Ethereum, for example, does not rely on probability alone: validators vote on checkpoint blocks every epoch, and once two-thirds of staked ETH agrees across two epochs (around 13 minutes), the block is economically finalized, meaning reversing it would require burning a huge share of all staked ether.

Until a transaction has enough confirmations, it remains vulnerable to a zero confirmation transaction double-spend attempt, which is why wallets, merchants, and exchanges wait for a minimum count that fits the value and risk involved before crediting funds.