Miner fees are paid by the sender to incentivize the bitcoin miners to include transactions in the blockchain
Bitcoin transactions are sent to the network with an extra fee attached. This fee is paid directly to the miner who adds the transaction to a block. Miner fees are based on the size of the transaction being sent in bytes. Miner fees are not impacted by the amount of bitcoin being spent.
The fee rate is generally measured in Satoshi/byte. A Satoshi is the smallest unit of bitcoin (0.00000001 BTC). For the purposes of this example, let's say a "standard" bitcoin transaction is around 250 bytes in size.
So, a standard transaction with a fee rate of 100 sat/b would be calculated as:
250 byte transaction * 100 satoshis = 25,000 satoshis = 0.00025000 BTC
Simply put, the more unspent outputs that are used to form a transaction, the larger the transaction will be in bytes. By default, Samourai creates larger transactions than average with some of its privacy features (such as STONEWALL). A larger transaction will consequentially incur slightly greater costs in miner fees for a given transaction. You can still configure Samourai to create the smallest possible transactions as needed.
When sending in Samourai, on the Send screen you will see a preview of your estimated fee directly beneath and to the left of the fee slider as you interact with it.
When sending your transaction, on the Send screen you will also see a summary of all fees listed in a popup/dialog box confirming your send for a final time after tapping the green Send button.
Samourai Wallet provides users with dynamic fee profiles based on current network conditions. From the send screen you are able to modify the fee profile used on a per-transaction basis using the fee slider. The fee slider features three different priority 'profiles', and these are based on how quickly you need the transaction to be added to a block. In bitcoin a block is usually produced roughly every 10 minutes.
This profile aims to have your transaction confirmed within the next 1-24 blocks
This profile aims to have your transaction confirmed within the next 1-3 blocks
This profile aims to have your transaction confirmed in the next 1-2 blocks.
Samourai is one of the only Bitcoin wallets to allow you to top-up the miner fee of transactions even after you have already sent them. This can be useful if you sent the transaction with a low custom fee resulting in a very long confirmation time. There are two main ways the wallet can achieve this.
RBF is a method of transaction boosting that replaces the 'stuck' transaction with a new one that pays a higher fee. Replace-by-fee must be toggled on within the Transactions settings of the wallet before broadcasting a transaction you may wish to later increase the fee on.
CPFP boosts a transaction by spending an output of the 'stuck' transaction back to the same wallet at a much higher fee. This creates a second 'child' transaction which is chained off of the original 'parent'. If a miner wants to collect the higher fee from the child transaction, they must also mine the parent transaction at the same time.
The following steps can be used for both inbound and outbound transactions.
To top up the transaction fee of the sent transaction simply tap the unconfirmed transaction in the main screen in Samourai. You will be taken to the Transaction Details screen.
On the bottom of the Transaction Details screen, tap the button labeled Boost Transaction Fee to begin the process. You will be asked to confirm the new miner fee before the boost is attempted.
Once you have sent the boost you will see a small transaction leave your wallet, this is the boost transaction. Both this boost transaction and your original stuck transaction should confirm within the next block.
If the wallet has RBF enabled, the 'Boost Transaction' option will always favour this method. Otherwise the wallet will attempt a CPFP.
If for any reason the wallet cannot boost a transaction using the method above, a manual CPFP may help. This is only possible with an outgoing transaction containing a change output or any inbound transaction.
Tap the receive button and copy the next receive addressto your phone's clipboard.
Long tap your wallet balance to open the unspection outputs list.
Tap the UTXO belonging to the stuck transaction then tap the icon.
Tap Spend, paste in the address from your clipboard and choose a miner fee equal to or higher than that required to enter the next block. You can see this here.
By default, Samourai Wallet errs on the side of increasing the blockchain privacy and plausible deniability of transactions. This focus has a side effect of increasing in the size of transactions created, thus increasing the overall cost of the miner fee when sending. The wallet can be fully configured for creating low fee transactions by following the steps shown below.
Tap the three vertical dots on the top right of the toolbar and then tap Settings. This will launch the wallet settings screen, where all configuration will take place.
From the main Settings screen tap the Transactions option. Disable the Receive change to like-typed outputs option by removing the checkmark from the checkbox. Like-typed outputs is a Samourai feature that improves your privacy on the blockchain.
STONEWALL is enabled by default for all transactions. You can disable STONEWALL when sending a transaction, on a per-transaction-basis, by toggling the STONEWALL toggle switch to the OFF position.
The toggle switch for STONEWALL is located on the Review Transaction screen, which is accessed by tapping the blue Review Transaction button on the bottom of the Send Screen in Samourai.
Disabling STONEWALL will result in much smaller transactions, at the loss of blockchain privacy.
From the Transactions settings screen Enable the Spend using RBF option by adding a checkmark to the checkbox. Enabling RBF will allow you to later top-up low transaction fees.
The wallet is now properly configured for creating low fee transactions at the sacrifice of some privacy and plausible deniability gains.