About RBF and CPFP

About RBF

RBF, short for Replace-by-fee, means unconfirmed transactions can be replaced by new transactions (with higher gas) . It is a mechanism that allows the sender of a transaction to increase the transaction fee before the transaction is confirmed. If a user sends a Bitcoin transaction but it remains unconfirmed for a long time due to low transaction fees, they can use the RBF option to increase the transaction fee, thus improving the transaction's priority. This can encourage miners to include the transaction in a block faster, thereby speeding up the transaction confirmation process.

Differences in RBF Transaction Types

Replace-By-Fee transactions have three different types: First-Seen-Safe (FSS) RBF, Full RBF, and Opt-in RBF.

FSS RBF requires that RBF transactions include the same outputs as the transactions they replace and consume the same inputs;

Full RBF means the transaction is simply a double spend of another transaction, but with a higher fee paid than the transaction it replaces;

Opt-in RBF means RBF transactions can only replace transactions that have opted in to allow themselves to be replaced.

About CPFP

CPFP, short for Child-Pays-For-Parent, is a mechanism that allows speeding up the confirmation of a set of transactions by increasing the transaction fee associated with its child transactions in an unconfirmed transaction scenario. If a user sends a transaction and the transaction's child transaction (typically a change transaction) does not have enough fees, the user can accelerate the confirmation of the entire transaction set by increasing the fees of the child transaction.