My withdrawal is stuck in the mempool. Can I cancel it or increase the fee?

You can use transaction accelerators or CPFP to increase your fee rate.

Bitcoin transactions can not be canceled. When you broadcast a transaction to the bitcoin network, it must be mined into a block on the blockchain to become confirmed. Until it’s confirmed, it will wait with other unconfirmed transactions in the mempool. Miners prioritize the transactions with the highest fee rate (sats/vb). As the global demand to move bitcoin fluctuates, so do fee rates.

If you broadcast a transaction with a low fee rate, your transaction can get stuck waiting for confirmation, possibly for days, weeks, or even longer. If you need to, you can pay more bitcoin to increase the prioritization of your transaction confirmation.

How to check if it makes sense to accelerate your transaction

1. Sign in to your Unchained account at my.unchained.com.
2. Navigate to your vault by clicking Vaults. Select the name of your vault that has a broadcasted withdrawal transaction.
3. In the Transact box, select View Transaction.
4. Click on the magnifying glass symbol to the right of your Transaction ID. This will open a new tab and show your transaction in mempool.space.
5. Look for the section that says ETA. If it says “not any time soon” you may want to take steps to accelerate your transaction. You can also compare your transaction’s fee rate (in sats/vb) to the suggested fee rate shown in mempool.space.
   
   
   
   

Method 1: Paying miners out-of-band

You can use a service such as Mempool Accelerator or ViaBTC transaction accelerator to pay additional fees directly to miners, who will accelerate your transaction.

For example, here are some steps if you decide to explore the Mempool Accelerator option:

1. Sign in to your Unchained account at my.unchained.com.
2. Navigate to your vault by clicking Vaults. Select the name of your vault that has a pending withdrawal transaction.
3. In the Transact box, select View Transaction.
4. Click on the magnifying glass symbol to the right of your Transaction ID. This will open a new tab and show your transaction in mempool.space.
5. Look for the Mempool Accelerator section. Here you will see the estimated cost and expected confirmation speed. If you wish to proceed, you can select Accelerate to view payment options.

Method 2: Child Pays for Parent (CPFP)

For some withdrawal transactions, you can use a method called child pays for parent, or CPFP. You can only utilize this method if your transaction includes change coming back to you. This is the most common situation unless you send your full vault balance at once. The goal of CPFP is to conduct another transaction that will spend the change from your original transaction with a higher fee rate.

To attempt a CPFP on your own, follow these steps:

Gather information using mempool.space.

1. Sign in to your Unchained account at my.unchained.com.
2. Navigate to your vault by clicking Vaults. Select the name of your vault that has a pending withdrawal transaction.
3. In the Transact box, select View Transaction.
4. Click on the magnifying glass symbol to the right of your Transaction ID. This will open a new tab and show your transaction in mempool.space.
5. Look for the section that says Fee. Note the number of satoshis. This is the Original Txn Fee, and you will use this information in a later step.
   
   
   
6. Scroll down to the bottom of the same page and look for Virtual Size. Note the number of vB. If the number is expressed in kvB, multiply it by 1000 to get the vB. This is the Original Txn vB and this information will be used in a later step.
   
   
   

7. Go to the homepage of mempool.space. Note the High Priority Rate (sat/vB). You will also use this information in a later step.
   
   
   

   Import your vault into Caravan.

8. Load your vault into Caravan to perform the CPFP.
9. Once you load your vault into Caravan, hit Send. Turn the Manual switch on to select which address you are spending funds out of.
   
10. Look for the address that says Pending in the Last Used column. This should be the address poised to receive your change from your original transaction. This is the address to spend funds out of, so check the box on the left side.
11. In the Address field, you can paste a deposit address from your vault or click the gray wallet icon on the right side, which will automatically apply one of your vault addresses.
    
    

    Calculate your new fee rate.

12. Next, you’ll need to enter a number in the Fee Rate field. To calculate the appropriate number, use the following formula and the information gathered from the earlier steps:
    
    
    
13. Take the Original Txn vB, and add 339. The 339 is a constant based on the vB of the CPFP transaction.
14. Multiply this result from Step 13 by the High Priority Rate on mempool.space.
15. Subtract the result of Step 14 by the Original Txn Fee (the total fee in sats, not the fee rate).
16. Divide the result of Step 15 by 339. Enter this number in the Fee rate field on Caravan.
    

    Complete and broadcast the transaction.

17. Once you’ve entered your fee rate, select the gray circle in the far right containing a plus sign. This amount of bitcoin will be sent back to your vault.
18. Select Preview Transaction, and follow the normal withdrawal steps to sign and broadcast the CPFP transaction.
19. You’re done! Both the CPFP transaction and the original transaction will now have an effective fee rate that approximately matches the recommended high fee rate, so they are mined quicker.