In Bitcoin, RBF stands for Replace-by-Fee. This feature allows a Bitcoin transaction to be flagged as RBF, enabling the sender to replace it with another transaction that includes a higher fee. This mechanism helps users respond to network congestion and unexpected fee increases.
If a user sends a transaction with a low fee and finds that it is taking too long to confirm, they can increase the fee to expedite the confirmation process.
RBF only works while the transaction is in the mempool, waiting for its first confirmation. Once a transaction is included in a block and receives its first confirmation, it can no longer be replaced.
Additionally, for a transaction to be replaceable, it must be marked as RBF-enabled when first sent—provided that the wallet or platform being used supports this feature. Not all wallets or platforms offer the RBF feature, so it’s advisable to check in advance if you plan to use it.