We are thrilled to share that coin control has finally arrived in Nunchuk.

A quick primer on coin control
When it comes to Bitcoin wallets, your balance isn't just a number, it's a collection of individual coins, also known as “UTXOs”. Think of it like the cash in your pocket: a few $10s, some $5s, and a handful of change. The total sum of all those bills and coins makes up your pocket money, just like your Bitcoin balance.

When you go and make a purchase, you might want to choose which coins to use, and which ones to keep for later. That's where coin control comes in. It's like organizing your pocket money - stacking your bills, separating your coins, and setting aside any worn or damaged bills for spending first.

With Bitcoin, you have coins of arbitrary values, so it's even more important to keep them organized. Coin control is the process of labeling, organizing, and picking which coins to use in transactions.

Since all Bitcoin transactions are public, coin control used properly can greatly improve your on-chain privacy. By mastering coin control, you'll be one step ahead in protecting your information.

Let’s look at how Nunchuk’s advanced coin control features work.

Transaction note
Every coin in your wallet has a story. It comes from a transaction - maybe someone sent you the coin, or maybe it's the "change" you got when you sent bitcoins to someone else. But no matter what, each coin is linked to a parent transaction.

In Nunchuk, each coin automatically inherits the parent transaction’s note as its own label.

What this means is that a lot of times, annotating the transactions is enough for organizing your coins.

We have given the transaction note some major improvements. Notes are now displayed inline in your transaction history and coin view, so you can quickly see all the details. They can support up to 280 characters, so you can add as much information as you need. And if you want to link your coins to external sites (such as a Lightning browser or any other layer 2 systems), you can do that too - just add a hyperlink to your note.


Coin tags

If you have a lot of coins, you might need more than just transaction notes to label and categorize your coins.

We introduce coin tags (inspired by the Twitter #hashtags), a great tool to organize your coins.

A coin can have any number of tags attached to it. Tags are color-coded, to help you quickly recognize coins from different categories.

Coin lock

A common action you might want to do with a coin is “locking” it, i.e. preventing it from being accidentally used in transactions.

You can now easily lock any coin. Or select a bunch of coins and lock them all up in one fell swoop by entering Selection Mode.

Coin list

We made coins a top-level UI element. The list of coins is readily accessible from the wallet’s main screen.

From there, you can quickly view how many coins you have, the value of each coin, when and how they were created, and their associated tags and collections.

Customizing transactions

The ultimate test of a coin control system is how well it allows you to quickly pick and choose which coins to use when crafting a transaction.

With a few simple taps, you can now customize transactions any way you want. Adjust fee settings, or manually select coins, all in one place.

We also added an advanced search and filters system. You can look up coins by notes, tags, partial or complete addresses, transaction IDs, amounts, dates, and much more. You can also do in-place lookups while crafting a transaction.

Our search and filters system makes coin control tasks a breeze, even if you own hundreds or thousands of coins.

Collections
What if you need even more ways to organize coins, such as automatic filtering?

We introduce collections.

Similar to tags, collections can contain any number of coins. What makes collections different from tags are their automated policies.

An example of an automated collection policy is to send new coins to a collection and lock them all up. They can stay locked until you have time to review and process them one-by-one. This makes sure you don’t accidentally spend any coins that you don’t want to.

Another example is to automatically tag all coins sent to a set of addresses with the same tag.

We’ll introduce more policies in subsequent releases.

Backing up coin control data

Last but not least, the ability to back up and recover your coin control data is essential.

Nunchuk supports two export formats for coin control out of the box: BIP329, and Nunchuk’s own format, which is an extension to BIP329 and has support for a richer feature set such as tags, locks and collections.

Summary
We have introduced several powerful coin control tools to help you better manage your wallet and take your privacy to the next level. We look forward to seeing how Bitcoiners utilize these tools. If you have any feedback or feature requests, please direct them to [email protected].