Definition
A confirmation is evidence of a transaction’s inclusion in the chain recognized by the network. In a common Bitcoin-style convention, the containing block provides the first confirmation and each subsequent block adds one. Pending transactions that have merely been broadcast do not yet have a block confirmation.
Why Counts Matter
Additional blocks make some history-reversal attacks more costly under proof of work. For example, inclusion at height 100 with a current tip of 102 corresponds to three confirmations under that convention. Exchanges and payment services choose acceptance thresholds based on their policies and the asset involved. These thresholds are service requirements, not universal protocol guarantees.
Key Considerations
Confirmation count and finality are not always the same concept. Some protocols use explicit finalization, and a transaction can be included before its block becomes finalized. A chain reorganization can reduce a count or remove a transaction from the accepted history. Also check execution success: an included contract call may have failed while still consuming fees. Waiting for confirmations cannot correct an incorrect recipient address.