How to use CPFP to accelerate transaction confirmation?

Child Pays for Parent (CPFP) prioritizes low-fee transactions by attaching them to high-fee parent transactions, potentially accelerating their confirmation.

Feb 21, 2025 at 02:48 am

Key Points

• Understanding Child Pays for Parent (CPFP)
• Selecting Ancestors for CPFP
• Calculating the Optimal Fee Bump
• Timing the Fee Bump
• Monitoring Transaction Confirmation

How to Use CPFP to Accelerate Transaction Confirmation

Understanding Child Pays for Parent (CPFP)

Child Pays for Parent (CPFP) is a technique used in cryptocurrency transactions to prioritize the confirmation of a low-fee transaction (the "child") by attaching it to a high-fee transaction (the "parent"). The parent transaction pays for the combined transaction fees, ensuring that the child transaction is processed quickly.

Selecting Ancestors for CPFP

Ancestors are the confirmation from parent transactions of the child transaction. To select suitable ancestors:

• High Confirmation Priority: Choose ancestors assigned to blocks that are close to being mined.
• Sufficient Fee: Ensure that ancestors have sufficient fees to cover the combined transaction fees.
• Inclusiveness: Select ancestors that have not been fully replaced, as they have a higher chance of being included in a block.

Calculating the Optimal Fee Bump

The fee bump is the additional fee attached to the child transaction to incentivize miners to process it before other pending transactions.

• Calculate the child transaction fee: Child_Fee = Virtual_Size * Reference_Fee_Rate
• Calculate the parent transaction fee: Parent_Fee = Virtual_Size * Bump_Fee_Rate
• Fee Bump = Parent_Fee - Child_Fee

Timing the Fee Bump

The timing of the fee bump is crucial for optimal results.

• Early Bump: Increase the child transaction fee before it enters the mempool to maximize its chances of being processed quickly.
• Late Bump: Wait until the child transaction is well within the mempool and the fee rates have risen significantly for a more efficient bump.

Monitoring Transaction Confirmation

Once the child transaction is sent with an increased fee, it is essential to monitor its progress.

• Confirmation Status: Regularly check the confirmation status of the child transaction using blockchain explorers.
• Transaction Tracking: Use tools like "Mempool.space" or "Blockchain.com" to track the transaction and identify any potential issues.
• Reapplication: If the child transaction does not confirm within a reasonable timeframe, consider reapplying the CPFP technique.

FAQs

What is RBF (Replace-by-Fee)?

RBF (Replace-by-Fee) is a feature supported by some cryptocurrencies that allows users to manually increase the fee of their pending transactions. However, it requires a compatible wallet with RBF enabled.

How does CPFP differ from RBF?

CPFP utilizes a second transaction to increase the fee, while RBF directly modifies the fee of the original transaction. CPFP is often more reliable, as miners are incentivized to include the parent transaction solely based on its high fee.

Can CPFP guarantee transaction confirmation?

No, CPFP does not guarantee transaction confirmation. It significantly increases the chances of confirmation by prioritizing the child transaction, but factors like network congestion and fee rates can still affect confirmation times.

Is CPFP available on all cryptocurrencies?

No, CPFP is only supported by cryptocurrencies that allow for dynamic transaction fees and permit multiple transactions to reference each other. For example, Bitcoin and Ethereum support CPFP.