Replace-by-Fee (RBF) is a Bitcoin protocol feature that allows users to modify an unconfirmed transaction by increasing its fee, helping it get prioritised by miners. This is useful when a transaction gets stuck due to low fees or network congestion. With RBF, the sender can essentially "replace" the original transaction with a new version that offers a higher fee, improving the chances of faster confirmation.

How RBF Works
A user broadcasts a transaction with RBF enabled.

If the transaction remains unconfirmed, the sender creates a new version with a higher fee.

Miners prioritise the updated transaction, dropping the original one.

Wallets That Support RBF
Electrum (Desktop) – One of the first to implement RBF.

Wasabi Wallet (Privacy-focused) – Supports RBF for better transaction flexibility.

Samourai Wallet (Mobile) – Offers RBF and other advanced Bitcoin tools.

Bitcoin Core (Full node wallet) – Allows manual RBF through its console.

BlueWallet (Mobile/Lightning) – Supports RBF for on-chain transactions.

Limitations & Risks
Not all wallets support RBF (e.g., many exchange wallets don’t).

Some merchants may reject RBF-enabled transactions due to double-spend risks.

RBF is a powerful tool for optimising Bitcoin transactions, especially during high-fee periods. Always check if your wallet supports it before relying on it.