Spent Unspent Transaction Outputs

Overview

Many of the first generation blockchains (such as Bitcoin and Litecoin) use unspent transaction outputs (UTXOs) to account for users’ funds. In these blockchains, whenever a transaction is made a new UTXO is created, indicating the input (where the funds came from) and the output (where funds are being transferred to).

Spent UTXOs refer to previously created ones used as an input transferred to one or more addresses. Spent UTXOs cannot be used as an input again in order to avoid the double spending problem.

💡 How can I use it?

Though the name may appear counterintuitive, Spent Unspent Transaction Outputs are a key component of Bitcoin transactions. These reflect the total number of UTXOs sent as input in transactions to one or more addresses. Therefore, these account for multi-output transfers arriving at two or more addresses. This indicator can be useful to put into context multi-output transactions versus single-output ones.