Replace-by-fee (RBF)

If the feeGlossaryTransaction fee (network fee)The amount a Bitcoin transaction pays to the miner. It depends on the transaction’s size in vbytes and the fee rate offered – not on the amount you send.On the learning path: Stage 5 · Step 4 – First withdrawal →In the glossary →× is too low and the network is busy, a payment can sit in the mempoolGlossaryMempoolThe buffer in which a node collects valid but still unconfirmed transactions until a miner includes them in a block. There is no central mempool – every node keeps its own.On the learning path: Stage 5 · Step 4 – First withdrawal →In the glossary →× for hours or days. With replace-by-fee (RBF), you follow it up with a new version that pays a higher fee.

How it works

The replacement spends at least one of the same inputs. For a simple payment, it has to offer a higher total fee and a higher fee rate than the original; nodes then swap out the old version.^[1],[3] As soon as one version is in a block, the other becomes invalid – you don’t pay twice.

Example when the network is busy: your payment is 141 vbytes and is waiting at 2 sat/vB (282 sats). You raise it to 10 sat/vB, so the new version pays 1,410 sats. Getting into the next block currently takes around 2 sat/vB.

Transactions used to have to signal that they could be replaced (opt-in, BIP 125).^[1] Since Bitcoin Core 28.0 of 2 October 2024, nodes running this software accept replacements of any unconfirmed transaction by default (‘full RBF’).^[2] You can still only use RBF if your wallet offers ‘bump fee’ – otherwise CPFPGlossaryCPFP (Child Pays for Parent)A way to speed up a stuck transaction: a follow-up transaction (the ‘child’) spends one of its outputs and pays a high fee. It then pays off for miners to include both transactions together.On the learning path: Stage 5 · Step 4 – First withdrawal →In the glossary →× often helps.

When receiving

A payment with 0 confirmations isn’t final: the replacement may have different recipients, so the sender can redirect the money. When selling to strangers, wait for at least one confirmationGlossaryConfirmationA transaction has one confirmation as soon as it is in a block; each further block adds one. With every confirmation, it becomes harder to displace the payment after the fact.On the learning path: Stage 5 · Step 4 – First withdrawal →In the glossary →×.