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Bitcoin Core psbtbumpfee RPC: Offline RBF Fee Guide
Bitcoin Core 0.21 psbtbumpfee guide covering wallet and mempool prerequisites, sat/vB fees, change handling, replacement policy, PSBT review and signing.
This guide explains Bitcoin Core psbtbumpfee RPC in plain English. It shows what the command does, what its result means and what it cannot prove.
TL;DR
- What it is: Bitcoin Core 0.21 psbtbumpfee constructs a replacement for an opt-in Replace-by-Fee wallet transaction and returns a PSBT rather than signing or broadcasting it. It keeps every original input, may reduce or create change and can add inputs when necessary.
- Why it matters: psbtbumpfee separates fee replacement construction from signing, which is useful for controlled custody. That safety exists only when operators verify the new fee, every output, any added input and the replacement state before authorisation.
- Current position: Require a second reviewer and explicit rollback or expiry, and pause payments, signing or network-dependent services until post-change evidence is complete.
What this means in simple English
An RPC is a command sent to one Bitcoin Core node. It can ask that node for information or request a local action. A successful reply describes that node; it does not automatically prove what happened across the Bitcoin network.
Beginners can focus on the input, the result and the limit of that result. Operators should test the command on the exact Bitcoin Core version they run before relying on it.
Simple example
Think of a mempool as one node’s waiting room for valid transactions that have not yet entered a block. Different nodes can have different waiting rooms, and the contents can change from one second to the next.
Key terms in plain English
- BIP:
- Bitcoin Improvement Proposal: a document describing a proposed rule, standard or process. Its status must be checked separately.
- Bitcoin Core:
- Widely used software that validates Bitcoin and can provide wallet, network and operator tools.
- RPC:
- A command that software sends to a node to request information or a local action.
- Mempool:
- A node’s changing local collection of valid, unconfirmed transactions.
- PSBT:
- A portable format for passing an unsigned or partly signed Bitcoin transaction between tools and signers.
Eligibility
The txid must identify an opt-in-RBF transaction in the selected wallet. Core fails when the wallet or mempool already contains a transaction spending an output of the original, so reconcile replacement state first.
Fee units
In 0.21 fee_rate is satoshis per virtual byte, replacing the pre-0.21 BTC-per-kilobyte unit. Pin the RPC version and reject ambiguous configuration during mixed-version migrations.
Estimator or explicit rate
Without fee_rate the wallet uses estimatesmartfee, optionally with a block confirmation target and economical or conservative mode. An explicit rate must satisfy replacement and incremental relay requirements.
Replacement construction
All original inputs remain. Core can reduce change, add inputs or create a new change output. Compare recipient scripts and amounts, input set, fee, vsize, locktime, sequences and change ownership.
Replaceable option
The default leaves the replacement BIP 125 replaceable. Setting false raises qualifying sequence numbers, but unconfirmed replaceable ancestors can still make practical replacement possible.
PSBT result
The response includes base64 PSBT, original fee, new fee and an errors array. It is a proposal, not evidence of signatures, broadcast, mempool acceptance or confirmation.
Signing workflow
Decode and analyse on a trusted node, show the fee delta and recipient invariants to approvers, sign using isolated devices, finalise, test mempool acceptance and broadcast once under idempotent controls. Build a revision-pinned evidence pack on an isolated node, wallet or protocol harness. Record source commit, binary hash, network, chain identity, configuration and dependencies.
Frequently asked questions
What is Bitcoin Core psbtbumpfee RPC?
Bitcoin Core 0.21 psbtbumpfee constructs a replacement for an opt-in Replace-by-Fee wallet transaction and returns a PSBT rather than signing or broadcasting it. It keeps every original input, may reduce or create change and can add inputs when necessary.
Is Bitcoin Core psbtbumpfee RPC active or supported today?
Require a second reviewer and explicit rollback or expiry, and pause payments, signing or network-dependent services until post-change evidence is complete.
Why does Bitcoin Core psbtbumpfee RPC matter?
psbtbumpfee separates fee replacement construction from signing, which is useful for controlled custody. That safety exists only when operators verify the new fee, every output, any added input and the replacement state before authorisation.
Do beginners need to use the technical details?
No. The command is mainly for people who operate Bitcoin Core or software connected to it. Other readers can use the article to understand what an operator or service is measuring.
Conclusion
psbtbumpfee separates fee replacement construction from signing, which is useful for controlled custody. That safety exists only when operators verify the new fee, every output, any added input and the replacement state before authorisation.
Primary sources
Check the current specification status and the documentation for the exact implementation you operate before moving production funds or changing a mining node.
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