Transaction ID (TXID)

Definition

A transaction identifier, commonly abbreviated TXID, is a hash-derived reference used to identify a cryptocurrency transaction. Bitcoin transactions can be looked up by TXID in a node or block explorer, and spending inputs refer to earlier outputs using the originating TXID together with an output index. A TXID is not a receiving address or a secret that authorizes spending. Its existence also does not prove confirmation, because a wallet can calculate an identifier before the transaction is mined or even broadcast. Bitcoin distinguishes the ordinary TXID from the witness transaction identifier for transactions using witness serialization. Changes to relevant transaction data can change the identifier, which matters when a wallet replaces an unconfirmed payment. When investigating a payment, verify the correct network, the actual recipient output, and its confirmation status rather than treating a pasted identifier or screenshot as complete evidence of settlement.