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What is replace-by-fee?
Replace-by-fee (RBF) is a Bitcoin feature that lets a sender replace an unconfirmed transaction with a new version paying a higher fee. Described in BIP 125, it lets a payment stuck with too low a fee be pushed through faster. The replacement must pay at least the original fee plus more.
What it means for you
If your bitcoin transaction is stuck, a wallet with RBF can raise its fee instead of waiting. The same feature means an unconfirmed incoming payment can still be replaced by the sender, so a zero-confirmation payment is not settled.
How it works
A transaction opts in when any of its inputs has an nSequence number below 0xfffffffe, and it also counts as replaceable while an unconfirmed ancestor signals. A node accepts a replacement only if it adds no new unconfirmed inputs, pays an absolute fee at least equal to the sum paid by the transactions it replaces, also pays for its own bandwidth at the node's minimum relay rate, and evicts no more than 100 transactions in total. Because the replacement spends the same inputs, only one version can ever confirm.
An example
Say you send a payment with a 500-sat fee and it sits unconfirmed. With RBF, your wallet signs a new version spending the same coins with a 2,000-sat fee. Nodes following BIP 125 swap the old version out, and only one of the two can confirm.
Source: BIP 125: Opt-in Full Replace-by-Fee Signaling · checked 4 October 2026
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