What Is Zero Confirmation?
Also known as: 0-conf, Unconfirmed Transaction, Zero-Conf
In short
Zero confirmation refers to a transaction that has been broadcast to the network but not yet included in any block. Because it waits in the mempool, it is not considered final and is theoretically exposed to double-spending risk.
In Bitcoin, after a transaction is sent, it first enters the nodes' memory pool (mempool) and waits for a miner to include it in a block. When it enters a block, it has received one confirmation; each subsequent block increases the confirmation count by one. Since the average block time is about 10 minutes, the first confirmation can take anywhere from a few minutes to much longer, depending on network congestion and the fee paid. For this reason, some merchants, especially for small payments, accept the transaction without waiting for confirmation; this is called a zero-confirmation (0-conf) payment.
The risk of this approach is that the sender may try to send the same coins back to themselves with another transaction that pays a higher fee. Because the Replace-by-Fee (RBF) feature allows an unconfirmed transaction to be replaced with a higher-fee version, it makes zero-confirmation transactions even less reliable. For this reason, crypto exchanges and large transactions wait for several confirmations.
Off-chain solutions such as the Lightning Network have been developed for the need for fast and final payment. On some blockchains that provide fast finality, transactions enter a block within a few seconds, so the zero-confirmation problem matters less.
Last updated: · This content is for information purposes only and is not investment advice.