Bitcoin Fee Bumping Tools Compared: Unstick Transactions

How Bitcoin Fee Bumping Works

A Bitcoin transaction gets stuck when its fee rate falls below what miners require for inclusion in the next block. During periods of high network congestion, a transaction broadcast at 5 sat/vB may sit unconfirmed for hours or days if the going rate climbs to 30 sat/vB or higher. Fee bumping is the process of increasing the effective fee rate so miners prioritize the transaction.

There are three approaches to unsticking a transaction: Replace-by-Fee (RBF), which replaces the original transaction with a higher-fee version; Child Pays for Parent (CPFP), which creates a new transaction spending an unconfirmed output at a high enough fee to cover both; and third-party transaction accelerators, which pay mining pools out-of-band to prioritize a specific TXID. Each method has different requirements, costs, and privacy tradeoffs.

For a detailed technical comparison of the two on-chain methods, see our RBF vs CPFP comparison tool.

Fee Bumping Methods at a Glance

Wallet RBF Support

Since Bitcoin Core 28.0 (October 2024), the full RBF mempool policy has been enabled by default. Bitcoin Core 29.0 (April 2025) removed the -mempoolfullrbf configuration option entirely, making full RBF unconditional. Any unconfirmed transaction can now be replaced by a conflicting transaction that pays a higher fee, regardless of whether the original signaled BIP 125 opt-in. This means the network-level barrier to RBF is gone: the remaining question is whether your wallet provides a UI or API to create the replacement.

Sparrow Wallet

Sparrow provides a dedicated fee bumping interface. Navigate to the Transactions tab, right-click the unconfirmed transaction, and select "Increase Fee." A slider lets you set the new fee rate. Sparrow also supports cancellation by replacing the transaction with one that sends all funds back to your own wallet. Sparrow enables RBF signaling by default on outgoing transactions.

Electrum

Electrum supports RBF through the History tab. Right-click an unconfirmed transaction, select "Increase fee," set the new rate, then sign and broadcast. Electrum can also perform CPFP: if you received a transaction and want to speed it up, you can spend the unconfirmed output with a high-fee child transaction. Electrum opts in to RBF by default for outgoing transactions.

Bitcoin Core

Bitcoin Core handles fee bumping via the bumpfee RPC command (or psbtbumpfee for PSBT workflows). The replacement spends the same inputs and pays the same recipients, reducing the change output to cover the additional fee. If the change would fall below the dust limit, Bitcoin Core may add inputs. The GUI wallet also provides a "Bump fee" button for unconfirmed outgoing transactions.

Other Wallets

BlueWallet, Blockstream Green, Nunchuk, and Trezor Suite all support RBF with dedicated bump-fee interfaces. Ledger Live (the consumer app) does not currently expose an RBF speed-up or cancellation feature: its internal documentation recommends importing the wallet into Electrum to perform fee bumps. Hardware wallets paired with Sparrow or Electrum inherit those wallets' full RBF capabilities.

Wallet Fee Bumping Compatibility

For a broader wallet comparison, see our wallet fee estimation comparison.

Third-Party Transaction Accelerators

Transaction accelerators work outside the normal fee market. Instead of replacing or supplementing a transaction on-chain, the service communicates directly with mining pool operators, asking them to prioritize a specific TXID. The accelerator charges a fee (paid via Lightning, fiat, or cryptocurrency), and partner pools treat the transaction as if it paid a higher fee rate when constructing their block templates.

Mempool.space Accelerator

The Mempool Accelerator launched in mid-2024 with partnerships across major mining pools including Foundry USA, MARA Pool, SBICrypto, SpiderPool, and Ocean. Together these pools represent roughly 40% of Bitcoin's global hashrate, giving accelerated transactions a meaningful probability of landing in the next block. Payment options include Lightning, Cash App Pay, Apple Pay, Google Pay, and preloaded account credit via on-chain BTC or Lightning. Acceleration bids are publicly visible on Mempool's block audit dashboard.

ViaBTC Accelerator

ViaBTC operates one of the longest-running accelerator services. It offers a free tier with limited submissions per hour and minimum transaction requirements (single transaction under 0.5 KB, fee rate at or above 0.0001 BTC/KB). The paid tier accepts BTC, BCH, or LTC. ViaBTC's pool mines approximately 13% of Bitcoin blocks, so an accelerated transaction has roughly a 1-in-8 chance of the next block being found by ViaBTC. Multiple blocks may need to pass before the acceleration takes effect.

Accelerator Limitations

Accelerators are not guaranteed to work. They only help when a partner pool finds the next block, and multiple pools must be partnered for reliable coverage. Acceleration requests typically cannot be modified once submitted. Some services may cancel requests without refunds to prevent transaction pinning abuse. The cost can also exceed what an RBF replacement would have cost, particularly during moderate congestion where a small fee bump would have sufficed.

Cost Comparison

The cost of unsticking a transaction varies significantly by method. RBF is almost always the cheapest option because the replacement transaction occupies the same block space as the original: you pay only the fee difference. CPFP adds a second transaction to the chain, so you pay for the child's block space (at minimum ~141 vB for a simple P2WPKH spend) plus enough fee to raise the combined package to the target rate. Accelerators charge a service premium on top of the fee delta.

As a worked example: suppose a 250 vB transaction was broadcast at 5 sat/vB (1,250 sats total fee) and you want to bump it to 30 sat/vB. With RBF, the replacement costs 7,500 sats total, an increase of 6,250 sats. With CPFP using a 141 vB child, the child must pay enough to bring the 391 vB package to 30 sat/vB, meaning a total package fee of 11,730 sats: the child alone pays 10,480 sats. Accelerators would charge the fee delta plus their service margin. For a deeper analysis of fee dynamics, see our research on Bitcoin fee market dynamics.

Privacy Tradeoffs

Each fee bumping method carries different privacy implications. RBF replacements reuse the same inputs, so they do not reveal additional UTXO ownership information beyond what the original transaction already exposed. However, the replacement may have a different change output amount, which can assist chain analysis in identifying the change output.

CPFP creates a visible on-chain link: the child transaction explicitly spends an output from the parent, confirming ownership of that output. If the recipient performs CPFP, it links the recipient's spending activity to the incoming payment. For privacy-conscious users, sender-side RBF is generally preferable.

Accelerators leave no on-chain footprint, but you share your TXID and payment details with the accelerator service. Mempool.space also makes acceleration bids publicly visible on its dashboard.

The Full RBF Policy Shift

The transition to full RBF has been one of the most debated policy changes in Bitcoin's recent history. Before Bitcoin Core 28.0, RBF was opt-in: only transactions that set the BIP 125 sequence number signal could be replaced. Merchants accepting zero-confirmation transactions relied on this: if a transaction did not signal RBF, they treated it as unlikely to be replaced.

With full RBF now unconditional in Bitcoin Core 29.0, any unconfirmed transaction can be replaced regardless of signaling. This eliminates the security assumption behind zero-conf acceptance for on-chain payments. Merchants handling high-value payments increasingly wait for at least one confirmation or use payment protocols like Lightning that provide instant finality. For more on this shift, see our research on full RBF's impact on merchants.

When to Use Each Method

Choosing the right fee bumping method depends on your role in the transaction and the tools available to you.

• You sent the transaction and your wallet supports RBF: use RBF. It is the cheapest and most straightforward option.
• You received the transaction and it has a spendable output: use CPFP. Create a child transaction spending the unconfirmed output at a high fee rate.
• Your wallet does not support RBF or CPFP: import your keys into Sparrow or Electrum, or use a third-party accelerator.
• The transaction is time-sensitive and you cannot perform on-chain fee bumping: use the Mempool.space Accelerator for its broad pool coverage.
• You want to avoid on-chain fees entirely for future payments: consider using Spark or Lightning for instant, low-cost transfers that bypass the on-chain fee market altogether.

Frequently Asked Questions

Can I speed up a Bitcoin transaction I did not send?

Yes, using CPFP. If the stuck transaction has an output paying you, you can spend that unconfirmed output in a new child transaction with a high enough fee to incentivize miners to confirm both. You cannot use RBF unless you control the sending wallet's private keys. Third-party accelerators also work for anyone who knows the TXID.

Is RBF or CPFP cheaper for fee bumping?

RBF is almost always cheaper. The replacement transaction occupies the same block space as the original, so you only pay the fee difference. CPFP requires an additional child transaction (at least ~141 vB for P2WPKH), and the child's fee must cover the shortfall for both parent and child combined.

Does Ledger Live support RBF fee bumping?

As of the latest available documentation, Ledger Live's consumer app does not provide a built-in RBF speed-up or cancellation feature. Ledger's own developer documentation recommends importing the wallet into Electrum to perform fee bumps. A Ledger hardware device paired with Sparrow or Electrum can perform RBF through those wallets' interfaces.

Do Bitcoin transaction accelerators guarantee confirmation?

No. Accelerators work by asking partner mining pools to prioritize a TXID, but they only help when one of those pools finds the next block. Mempool.space partners with pools representing roughly 40% of hashrate, giving reasonable odds per block. ViaBTC controls about 13% of hashrate. Neither guarantees confirmation in a specific timeframe.

What happened to opt-in RBF in Bitcoin Core?

Bitcoin Core 28.0 (October 2024) changed the -mempoolfullrbf default to enabled, and Bitcoin Core 29.0 (April 2025) removed the option entirely. Full RBF is now unconditional: any unconfirmed transaction can be replaced by a higher-fee conflicting transaction, regardless of BIP 125 signaling. The opt-in mechanism is no longer relevant at the network policy level.

Can I cancel a Bitcoin transaction using RBF?

Yes. An RBF "cancellation" works by broadcasting a replacement transaction that sends all funds back to your own wallet. Wallets like Sparrow, Electrum, and Bitcoin Core support this. The replacement must pay a higher fee than the original. Once the replacement confirms, the original transaction is invalidated.

How does fee bumping affect transaction privacy?

RBF has minimal privacy impact since it reuses the same inputs, though the changed fee amount may help identify the change output. CPFP creates an explicit on-chain link between parent and child transactions, revealing UTXO ownership. Accelerators leave no on-chain trace but require sharing your TXID with the service provider.

This tool is for informational purposes only and does not constitute financial advice. Wallet feature availability may change between software versions. Always verify current capabilities in your wallet's documentation before relying on fee bumping features.