Full RBF

Full RBF means a node accepts any fee-bump replacement of an unconfirmed transaction - regardless of whether the original signaled BIP-125 opt-in RBF. In other words, all unconfirmed transactions are treated as replaceable.

Bitcoin Core enabled full RBF behavior optionally starting in v24 (late 2022) and made it the default in v26 (late 2023). By 2026, a substantial portion of the node network runs full RBF, meaning the practical guarantee that "an unsignaled transaction won't be replaced" no longer holds.

The argument for full RBF:

• It simplifies fee policy. Wallet implementations no longer need to track or care about the RBF-signaling bit.
• It reflects the underlying reality. Miners always could mine whichever conflicting transaction paid them more; opt-in RBF was a relay-layer politeness, not a consensus rule.
• It improves user experience for senders who need to bump fees.

The argument against:

• It further erodes zero-confirmation payments. Merchants relying on "I saw it in the mempool" for instant settlement have to either wait for one confirmation or accept the risk of a replacement attempt.
• It shifts the burden of "is this safe to act on?" onto merchants and exchanges, who must wait for confirmations.

The pragmatic landscape in 2026: zero-conf was always weakly secure; full RBF just made the weakness obvious. The practical answer for instant payments is Lightning, which is genuinely instant and final. For on-chain, wait one confirmation. The era of "I'll trust an unconfirmed transaction because most people don't RBF" is ending.

See Replace-by-Fee (RBF) for the opt-in flavor full RBF extends.