Definition
A transaction ID (TxID) identifies a transaction. Many blockchains derive it cryptographically from transaction data, so it is often called a transaction hash. The exact calculation and included fields depend on the protocol. An exchange’s internal order number or withdrawal reference is not necessarily an on-chain TxID.
How It Is Used
A user can enter a TxID into a suitable block explorer or query a node to inspect transaction details. The result may show status, block inclusion, addresses, fees and execution information. The network must be correct: an identifier is not a universal cross-chain tracking number. On Bitcoin, transaction identifiers and witness transaction identifiers also serve distinct purposes.
Key Considerations
Receiving a TxID does not alone prove a completed payment. A transaction may be pending, rejected, replaced or absent from the accepted chain. Verify status and relevant outputs or token-transfer records. Publicly sharing an identifier can reveal transaction details and link activity to a person. A screenshot containing a hash is weaker evidence than checking the actual network record.