What is coin control in bitcoin?

Coin control is a wallet feature that lets you choose exactly which coins a bitcoin transaction will spend. Without it, the wallet picks coins automatically. With it, you can pick, label or freeze individual coins, which matters for both privacy and fees.

What is UTXO selection?

Bitcoin does not hold a single account balance. As COLDCARD explains, your balance is the sum of unspent transaction outputs, or UTXOs, each one created by a past payment to you. When you send bitcoin, the wallet must pick one or more of these as inputs. Each one is spent in full, and any excess comes back as change, explained in what a change address is. The basics of UTXOs are in what a UTXO is.

Automatic selection follows the wallet's own rules. Coin control hands that choice to you.

How does Bitcoin Core coin control work?

In the Bitcoin Core desktop app, coin control is an option you switch on in the settings. Once enabled, you can choose specific coins when you send. If you enable it but select nothing, the wallet still chooses coins automatically, as a Bitcoin Core GUI issue on GitHub points out.

Bitcoin Core also has a lockunspent command that locks chosen outputs so automatic selection skips them. As of November 2026, the version 30.0 docs say locks live in memory by default, and a persistent option saves them to the wallet file so they survive a restart. Bitcoin Core 24.0 added a sendall command that spends selected coins in full without creating change. Other wallets, such as Sparrow, show a tab listing each UTXO with its label, value and age.

How does coin control help privacy?

When a transaction spends several coins together, observers can assume they belong to the same owner. COLDCARD notes that this link cannot be undone once the transaction is broadcast. The Bitcoin Wiki gives an example of someone paid in bitcoin by an employer who also buys bitcoin with cash. To donate privately, that person can spend only the cash-bought coins, so the employer cannot tie the donation to their wages.

Common habits include labeling each coin by where it came from when you receive it, and freezing coins you do not want to spend, such as tiny unrequested deposits that may be part of a dusting attack.

How can coin control lower fees?

On-chain fees are based on transaction size, and every input adds size. COLDCARD estimates about 68 vbytes for each native SegWit input, so spending many small coins costs more than spending one large one. Some users merge small coins when fees are low to cut future costs, ideally only coins from the same source to avoid linking histories. A coin is called dust when the fee to spend it is higher than its value, which can happen as fee rates rise. Coin control lets you leave such coins out of a payment when fees are high.