Custom fees let you enter your own Bitcoin fee rate or Ethereum gas price when preparing a transaction in the BitBoxApp. To use them, turn on Enable custom fees under Settings → Advanced settings, then choose Custom under Priority on the send screen.

If you are unsure which value to enter, use one of the app's automatic fee priorities instead. The available priorities and their estimates depend on the account and the fee-estimation service. Confirmation times are estimates, not guarantees.

Enable custom fees

This setting adds a manual fee option when preparing a payment; turning it on does not send a transaction.

1. Open Settings in the BitBoxApp.
2. Select Advanced settings.
3. Turn on the switch beside Enable custom fees.

You can now select Custom under Priority when sending from a Bitcoin or Ethereum account. Automatic priorities remain available when the app can provide estimates.

Set a custom Bitcoin fee

For Bitcoin, you enter a fee rate in sat/vB (satoshis per virtual byte). This is not the total fee: the total also depends on the transaction's virtual size. Check current fee-rate estimates on mempool.space close to the time you plan to send.

1. Open the Bitcoin account you want to send from and select Send. The Send Bitcoin screen opens.
2. Enter the recipient's address and the amount you intend to send.
3. Under Priority, select Custom. A Fee rate field appears.
4. Enter your chosen rate in Fee rate, using sat/vB. Wait for the app to calculate the Network fee below the priority controls, then check that amount before proceeding.

The displayed Network fee shows the calculated fee for this transaction at your chosen rate. Two transactions can have different total fees even when you enter the same sat/vB value.

Set a custom Ethereum fee

For Ethereum, you enter a gas price in Gwei. This controls the price per unit of gas, rather than the total fee in ETH. The app estimates the gas required for the transaction and calculates the network fee. Check current gas-price estimates on the Etherscan Gas Tracker; do not enter another transaction's total ETH fee into the gas-price field.

1. Open the Ethereum account you want to send from and select Send. The Send Ethereum screen opens.
2. Enter the recipient's address and the amount you intend to send.
3. Under Priority, select Custom. A Gas price field appears.
4. Enter your chosen value in Gas price, using Gwei. Wait for the app to calculate the Network fee below the priority controls, then review the fee shown in ETH before proceeding.

The custom-fee option provides one gas-price field; it does not offer separate maximum-fee and priority-fee controls.

Review the transaction before sending

Your custom value is now applied to the transaction you are preparing. Entering it does not send the payment. If you continue, review the recipient address, amount and network fee, and verify the transaction details on your BitBox02 before confirming. Cancel if anything differs from what you intended.

Network fees do not go to BitBox. For more about how fees are calculated, see What are blockchain network fees?

If a transaction is already pending

Changing the custom-fee setting does not change a transaction you have already sent. Do not send a separate payment just because the original is delayed: both payments could confirm.

• Bitcoin: start with Why is my Bitcoin transaction pending? to check whether any action is needed. If you need to increase the fee of an eligible unconfirmed transaction, follow the Sparrow and BitBox02 fee-increase guide.
• Ethereum sent through the BitBoxApp: follow the guide to speeding up a BitBox02 transaction with Rabby.