Zero Confirmation
transaction · security
A transaction observed before any block has included it.
- Also known as
- zero-conf, 0-conf
A zero-confirmation transaction has been broadcast or observed but has not been included in a block. A node may have checked it against consensus and mempool policy, yet another valid conflict can still win confirmation.
Risk depends on transaction value, goods delivered, propagation, conflicting spends, replacement policy, miner incentives, wallet detection, and the attacker's ability to obtain value before confirmation.
Double-spend proofs, pre-consensus systems, merchant risk engines, and direct node monitoring can improve detection or confidence. They do not turn an unconfirmed transaction into a block-confirmed one.
Related terms
Unconfirmed Transaction
→A transaction seen by the network but not yet included in a block, so its confirmation count is zero.
mempool · fees
Confirmations
→The count of blocks confirming a transaction, usually including the block that first contains it.
security · blockchain
Mempool
→A node's local set of unconfirmed transactions accepted for possible relay and block inclusion.
blockchain · node
Double Spend
→A double spend is an attempt to spend the same coins twice by getting one conflicting transaction accepted over another.
scam · security · blockchain · technical
Replace By Fee (RBF)
→A mempool policy that can accept a conflicting unconfirmed transaction when the replacement satisfies fee and relay rules.
bitcoin · policy · fees