Replace-by-Fee (RBF) Bitcoin Optech.

Replace-by-Fee is a node policy and there are many Bitcoin nodes that can set up own rules for their mempools.

There are Opt-in RBF and Full RBF. Opt-in RBF uses BIP 125 and usually we have to broadcast our transactions with opt-in RBF to bump fee later.

There are nodes and mempools that accept Full RBF that does not use BIP 125. They will accept Full RBF unconfirmed transactions to be replaced. But to avoid troubles, using opt-in RBF is better.

Opt-in RBF is enabled by default and there is proposal to enable Full RBF by default too.
https://bitcoinops.org/en/newsletters/2023/08/09/#full-rbf-by-default