From the release of v1.4.0, Envoy users can leverage full coin management within all of their hot or cold accounts. This includes:
Bitcoin transactions are made up of inputs and outputs. When an amount of sats is transacted from Alice to Bob, that amount will be comprised of one or more coins (inputs) from Alice's wallet. If Alice creates this spend by simply entering the amount to be sent and pressing go, her wallet will be performing 'coin control' on her behalf (usually based upon a pre-determined algorithm unique to each wallet type).
If Alice were to select the coin(s) she wanted to be used to send to Bob before pressing send, she would be said to be using 'Coin Control'.
TLDR - You have 10x $1 notes in your wallet and need to pay a $6 bill. Coin control is choosing which of those $1 notes you use to pay instead of allowing your wallet to pick them for you.
When a user has a wallet account that they are using for many different types of transactions, the wallet can quickly accumulate coins with varying histories. In this scenario, the user may not find it desirable to show common ownership of some of these coins by allowing them to be spent together.
Without coin control, it is impossible to ensure that the wallet will not combine such coins when constructing spends.
Once coins are categorized using tags and/or notes, a user can make educated decisions when constructing spend transactions such that they show common ownership of only the coins they choose. This is a powerful technique that can preserve your privacy when interacting with Bitcoin.
Before a user can use coin control effectively when spending, there must be some way to categorize coins. In Envoy, this is achieved by using Tags. A Tag is a user defined label or category that can be applied to each coin.
Some basic rules around Tags:
Applying a tag to a coin or multiple coins is simple:
To delete an entire tag, simply open the tag, tap the three horizontal dots in the top right corner, then tap Delete Tag.
If a Tag is not empty when it's deleted, the coins within fall back to the 'Untagged' Tag
To edit the name of a tag, simply open the tag, tap the three horizontal dots in the top right corner, then tap Edit Tag Name.
To retag a coin or multiple coins from an existing tag:
Locking tags or coins will prevent them from being used in transactions. Locking items can act as another form of coin control that allows you to quickly create simple spends that exclude only certain coins or tags from your wallet.
To lock a tag or coin:
The lock on the tag summary card will only show as locked if all coins within are locked.
Notes are a secondary piece of information that can be applied to a coin or transaction. Notes can be useful to add additional context to the existence of a coin or transaction within your wallet.
For example, you might have a coin in your 'Groceries' tag that was the change output of a spend at Walmart. You might find it useful to apply a note to that coin or transaction that says 'Walmart change', that gives you context on that specific coin without the need to create a brand new tag just for Walmart spends.
Notes applied to a transaction will be shared with all coins involved. Notes applied to a coin will be shown in the transaction details view.
To apply a note to a coin:
To apply a note to a transaction before sending:
Note that if you do not complete this manually, Envoy will prompt you to add a note when you press send. If you have no interest in using the notes feature, you can permanently dismiss this prompt.
To apply a note to an existing transaction:
Once you have your coins tagged, there are multiple ways in which you can practice coin control within Envoy. You do not need to choose a single one. These approaches can be used interchangeably depending on your requirements and apply to mobile wallet and Passport accounts alike.
If you find yourself in a position where you want to make a spend, perhaps to a recipient that you are less concerned about learning some of your wallet's coin history, spending from a tag or multiple tags is perfect.
Spending from tag(s) is a very simple and quick way to construct a transaction from a certain category of your wallet, without painstakingly considering the finer details of your coin history. It's the equivalent of talking to your wallet and saying:
"Spend X amount of sats to Bob. I don't care how you construct the transaction, but choose coins ONLY from this category."
To send from a tag or multiple tags:
Certain spends sometimes require more granular control of the individual coins used to construct a transaction. This might be because some coins have a history that you do not want shared with any other coins within your wallet.
To send from a single coin or multiple user-selected coins:
After constructing a spend, even without using coin control, Envoy allows you to check and edit the tags and/or coins involved in the transaction before broadcast.
To edit the tags or coins involved in a transaction: