Bitcoin UTXOs and coin control
Choose transaction inputs deliberately, understand change and balance fee efficiency against privacy.
The quick answer
A UTXO is an unspent transaction output. Your wallet balance can contain many UTXOs; coin control lets you choose which ones a payment spends.
Inputs are spent in full
A transaction consumes selected outputs and creates new ones. The remainder normally returns as change. Combining inputs can reveal a connection between them and increases transaction size.
Step by step
- 1
Label incoming outputs
Record their source privately in your wallet. Distinguish donations, exchange withdrawals and other payment histories.
- 2
Select the needed inputs
Use your wallet's coin-control interface. Compare the proposed payment, change, virtual size and fee before signing.
- 3
Verify the change
Make sure the signer recognizes your change policy. Review unexpected outputs and keep the new change output's history in your records.
Worked example
A selected 120,000-sat UTXO can fund a 70,000-sat payment, a 1,000-sat fee and 49,000 sats of change. The original UTXO no longer remains unspent.
Before you continue
A related question
Can I spend only part of a UTXO?
Not directly. You spend the whole output and create new outputs, usually including change back to your wallet.
Try it with a tool
Sources & further reading
Source links checked on 15 Oct 2026. Examples explain the mechanics; provider fees and features can change.
- Bitcoin Developer Guide developer.bitcoin.org
- Bitcoin.org bitcoin.org
