Block Confirmations

Block confirmations count how many blocks have been added to a blockchain since the block containing your transaction. Zero confirmations means the transaction is broadcast but not yet in a block; each additional block makes reversing it progressively harder, because an attacker would have to rebuild that much chain history. Exchanges set a required confirmation threshold before crediting a deposit, and the number differs by asset and by network because block times and reorganisation risk differ. That is why the same deposit can appear in a block explorer within seconds yet remain uncredited for a while. Some chains use deterministic finality instead, where a block becomes irreversible after a defined step rather than by accumulating confirmations.