Bitcoin developers plan to remove legacy RBF flag for privacy coordination
**Title:** Bitcoin Core Moves to Remove Legacy RBF Flag, Pushes for MAX‑2 as Wallet Default
Bitcoin Core contributor rkrux has proposed removing the legacy opt‑in Replace‑by‑Fee (RBF) signal from wallet transactions, arguing it is redundant now that full‑RBF is the network’s default mempool policy.
The move is more than code cleanup. It’s a coordinated privacy effort requiring all wallets to align on a single nSequence value. Without this, removing the BIP125 flag could create distinct transaction fingerprints, exposing on‑chain wallet identities.
The legacy RBF flag, introduced in Bitcoin Core 0.12.0 in 2016, let users voluntarily fee‑bump unconfirmed transactions. Since version 24.0, full‑RBF replaces any transaction regardless of nSequence, making the signal operationally obsolete.
Community voices like Murch and Electrum’s SomberNight favor **MAX‑2** as the ecosystem default. Data from Bitcoin Optech shows MAX‑2 is already used in about 75% of transactions, avoiding new fingerprints and preserving anonymity.
Alternatives such as MAX‑1 were dismissed because they would visually distinguish Bitcoin Core transactions from the majority. MAX‑2 is also seen as future‑proof for upcoming nVersion=3 and Package RBF upgrades, which will reserve MAX and MAX‑1 for specific behaviors.
For merchants, the visible opt‑in flag is gone, but fee‑bumping remains. Zero‑conf acceptance must treat all unconfirmed transactions as replaceable — already the correct stance since full‑RBF adoption.
If the PR is merged and wallets standardize on MAX‑2, it will mark a rare cross‑wallet default alignment, contrasting with the fragmented rollout of full‑RBF.
More on full‑RBF policy: Bitcoin Optech RBF documentation.
