Confirmations
security · blockchain
The count of blocks confirming a transaction, usually including the block that first contains it.
Confirmations count how deeply a transaction is buried in the chain. Most wallets count the block containing the transaction as 1 confirmation; each additional block built on top adds one more.
More confirmations reduce the chance that a transaction will be reversed by a chain reorganization. The appropriate number depends on the chain's security, the payment value, the recipient's risk tolerance, and whether instant acceptance is worth the risk.
Confirmations can decrease if the block containing a transaction is removed in a reorg. Transactions usually return to the mempool if still valid, but they may need to be mined again.
Related terms
Block
→A batch of valid transactions added to a blockchain, linked to the previous block by a cryptographic hash.
mining · blockchain · security
Block Height
→The position of a block in a blockchain, counted from the genesis block at height zero.
blockchain
Transaction
→A serialized state transition that a blockchain can validate, relay, and include in a block.
blockchain · technical