Glossary · UTxO

UTxO.

Unspent Transaction Output. A discrete chunk of value sitting at an address, consumable in full by a future transaction.

Think of it as

Think of UTxOs as digital banknotes, with any value, not fixed denominations. You can't spend half a €50 note, you hand over the whole thing and get change back.

In depth

A UTxO (Unspent Transaction Output) is the fundamental unit of value in the UTxO accounting model. Instead of holding a single mutable balance, a wallet holds a set of immutable outputs from prior transactions. Each spend consumes whole UTxOs and creates new ones.

Example

Sending 5 ada from a 10 ada UTxO consumes the entire 10 ada and creates two new UTxOs: 5 ada for the recipient and 5 ada (minus fee) of change back to you.

Try it interactively See UTxOs flow through transactions

Next on this path

  1. Change output A new UTxO that returns the leftover value to the spender after a transaction.
  2. eUTxO Extended UTxO. Cardano’s ledger model: a UTxO can carry datum and be locked by a script, enabling smart contracts on a UTxO chain.
  3. Coin selection The wallet’s job of picking which UTxOs to spend for a given target amount.