UTX

UTX is an acronym that can refer to several unrelated terms. In the context of digital currencies and blockchain, UTX most commonly denotes Unspent Transaction Output; in practice, the standard term is UTXO (unspent transaction output), but the plural or shortened form UTX is sometimes used in documentation or discussions. This article covers the blockchain-related usage.

A UTXO is a discrete output of a previous transaction that has not yet been spent. Each transaction consumes existing UTXOs as inputs and creates new outputs. The value of a UTXO is fixed when created and can be spent only in accordance with the output's locking script.

The set of all current unspent outputs forms the UTXO set, which a full node maintains to validate new transactions. To spend a UTXO, a user must provide a script signature satisfying the output's conditions. A transaction's inputs total must cover the outputs' value plus transaction fees.

The UTXO model contrasts with account-based models used by some networks. Benefits include straightforward parallel validation and fungibility across outputs; design can improve privacy by breaking direct one-to-one traces, though linkability remains a concern.

Notable implementations: Bitcoin and Litecoin use a UTXO-based model. Cardano uses an Extended UTXO (EUTXO) model to support more complex smart contracts. Other currencies may adapt UTXO variants or hybrid approaches.

Other uses: Outside blockchain, UTX can refer to other organizations or terms; this article focuses on the blockchain concept. UTX is not a single standardized term beyond its primary use as shorthand for unspent transaction outputs.