Glossary · UTxO

Change output.

A new UTxO that returns the leftover value to the spender after a transaction.

Think of it as

Change at the till. Hand over a 50 to pay for a 20, get back two new notes (a 20 for the seller, the rest as change) rather than a modified 50.

In depth

Because a UTxO is consumed in full, any value beyond the target plus fee is returned to the spender as a new "change" UTxO. A change output is needed whenever the selected inputs exceed the payment plus fee. If they match exactly, the transaction simply has no change output.

Example

Paying 3 ada from a 10 ada UTxO yields a 3 ada output to the recipient and a roughly 6.83 ada change output back to you (after fees).

Next on this path

  1. Coin selection The wallet’s job of picking which UTxOs to spend for a given target amount.
  2. Dust A UTxO so small that spending it eats a large share of its value in fees.