BTC - RBF and stuck transactions in the mempool

Bitcoin Replace-By-Fee (RBF) is a feature that allows you to replace a stuck or unconfirmed Bitcoin transaction in the mempool - a temporary storage area for pending transactions, with a new one that includes a higher transaction fee.

RBF is particularly useful during times of network congestion when transactions might take longer to get confirmed due to high demand.

How Does Replace-By-Fee (RBF) Work?

When you broadcast a Bitcoin transaction, a transaction fee comes along with it to incentivize miners to include the transaction in the next block.

However, if the network becomes congested, or if the initial fee is too low, the transaction might get stuck in the mempool. With RBF, you have the option to increase the transaction fee on an unconfirmed transaction, making it more attractive for miners to prioritize it.

Replacing a Stuck Transaction using RBF

To replace a transaction that's stuck in the mempool using RBF, follow these steps:

1. Check Transaction Status: Use a blockchain explorer or wallet software to monitor the status of your original transaction. Make sure it is still unconfirmed and stuck.
2. Confirm RBF is enabled: Look for the RBF flag in the tx on a BTC mempool explorer.
3. Create a Replacement Transaction: Create a new transaction with the same inputs as the stuck transaction but with a higher fee. This is essentially a "double-spend" transaction but with a higher fee. The higher fee incentivizes miners to prioritize the new transaction.
4. Broadcast the Replacement Transaction: Once the replacement transaction is created, broadcast it to the Bitcoin network. Miners will see the higher fee and prioritize it.
5. Wait for Confirmation: Monitor the replacement transaction to see if it gets confirmed in a block. If miners prioritize the new transaction, it should confirm relatively quickly.

📘

Via Tatum, only transactions submitted through RPC calls can enable RBF. For additional information on RBF, check the following guide. Alternatively, see our CPFP article.

Things to Watch Out using RBF

RBF transactions let you adjust fees after sending a transaction, but there are a few drawbacks to keep in mind:

• Unrestricted Modifications: RBF isn’t strictly for bumping fees—you can add new inputs or even change outputs when replacing a transaction. This flexibility can make RBF feel less reliable in certain cases, like 0-confirmation processing, where the transaction needs to stay exactly as it was first sent.
• Increased Risk of Mempool Eviction: When the network is congested, an RBF transaction may face eviction from the mempool, sometimes with a higher priority than other transaction types. This could result in delays if a new, higher-fee transaction replaces it in the mempool.
• Original Transaction Inclusion Uncertainty: There’s a chance the original transaction will be added to a block before the replacement gets fully propagated across the network. So, until one version is confirmed, there’s no way to be sure which one will make it into a block.