Fujn is an active Bitcoin transaction-acceleration service, but the claim that it is “the leading” accelerator is not backed by an independent ranking or verified success-rate data. It offers free TXID submissions subject to eligibility limits and a paid priority service. If your transaction is stuck, check your wallet’s RBF or CPFP options first; these may raise its mining incentive without paying an accelerator. Fujn may be worth considering when those options are unavailable, but confirmation is never guaranteed and crypto payments are generally irreversible.
The title’s 2025 framing is historical. Fujn’s current features and conditions can change, so verify the live instructions before submitting or paying.
What is Fujn?
Fujn is a website that accepts a Bitcoin transaction ID (TXID) for an acceleration request. The goal is to help a valid, unconfirmed transaction get included in a block sooner, typically by making it visible to more nodes, requesting priority from participating miners, or both. Fujn advertises free submissions and a paid “Priority Service” at fujn.com.
Fujn says it was founded in San Francisco in 2020 and works with mining-pool partners. Those are company statements, not independently verified facts. Its claim to use 81% of network hash power and its claim that most transactions confirm within 13 minutes are also unverified; neither should be treated as a performance guarantee.
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Fujn also offers a separate crypto-swap product. Its swap page describes fixed-rate and floating-rate options with operator fees of 0.5% and 0.4%, respectively, excluding network fees. Those terms belong to Fujn Swap, not Bitcoin acceleration; a swap is not required to submit a transaction for acceleration. See Fujn Swap for its current terms.
Why a Bitcoin transaction gets stuck
After a wallet signs and broadcasts a transaction, Bitcoin nodes can hold it in their mempools while miners select transactions for blocks. A transaction with no confirmations has not yet been included in a block. A low fee rate relative to competing transactions, network congestion, limited propagation, unconfirmed parent transactions, or a conflict with another spend can all delay or prevent confirmation.
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Zero confirmations do not mean a payment is final. Bitcoin’s developer guidance warns that competing or double-spend transactions can exist before confirmation; do not treat an unconfirmed payment as automatically safe. See the Bitcoin Developer Guide to payment processing.
How accelerators and wallet fee bumps differ
Rebroadcasting
A service can send an already-signed transaction to additional nodes. That may help if the transaction has not propagated well, but rebroadcasting does not change the transaction’s fee rate or compel miners to include it.
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Out-of-band miner priority
An accelerator may arrange an additional payment or priority request with participating mining pools. The original transaction stays unchanged, but a participating pool may choose to include it. Mempool describes its accelerator as using an out-of-band fee with mining-pool partners; the request is distinct from changing the on-chain transaction fee. See Mempool Accelerator.
RBF: replace the transaction with a higher-fee version
Replace-By-Fee (RBF) lets an eligible unconfirmed transaction be replaced with one paying a higher fee. Use the sending wallet’s own “Bump fee,” “Speed up,” or equivalent control when available. Bitcoin Core’s bumpfee operation requires the transaction to be in the wallet and eligible for replacement. See the Bitcoin Core bumpfee reference.
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CPFP: pay more through a child transaction
Child-Pays-for-Parent (CPFP) uses a new transaction that spends an unconfirmed output and pays enough fee to make miners more interested in confirming the parent and child together. It generally requires control of a spendable output and a wallet that can create the child transaction. Mempool outlines when RBF, CPFP, or an accelerator may be appropriate in its stuck-transaction guidance.
What Fujn advertises—and what that means
Fujn’s terms and thresholds below are claims on its own site, not a guarantee that a transaction will be accelerated. Check the live page before acting because eligibility, quotas, and prices may change.
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- Free route: Fujn advertises up to 20 free submissions per hour for transactions no larger than 0.5 KB and with a fee rate of at least 0.0001 BTC/KB. It says free requests are processed in submission order and priority is associated with ViaBTC-generated blocks. The free quota may be exhausted, so do not assume a slot will be available. ViaBTC’s own accelerator page displays the same size and fee-rate thresholds, while its support article discusses a 20-per-hour free allowance. The live availability and stated quota can differ.
- Paid priority: Fujn says its priority service has no transaction-volume or minimum-fee limit and uses relationships with multiple mining pools. The retrieved page did not establish a stable public price; review the amount and conditions shown on the live site before paying.
- Timing: Fujn’s FAQ gives a rough estimate of 10 minutes to one hour, often within an hour, but says timing is not guaranteed. A pool cannot control exactly when it finds a block, and other pools may not honor a request. ViaBTC likewise says timing depends on block generation.
Fujn’s page displays payment instructions for several cryptocurrencies. Do not rely on an address copied from an old page or third party: verify the destination, amount, network, and payment purpose on the live official page before sending. The retrieved information does not establish a fixed fee or a universal refund policy for Fujn’s paid service.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to decide what to do about a pending transaction
- Get the TXID. Find it in the sending wallet or ask the exchange or payment service that initiated the transfer. A wallet showing “pending” without a TXID is not enough to submit an acceleration request.
- Check that it exists. Search the TXID in a reputable block explorer. If it cannot be found, ask the sender whether it broadcast the transaction and request the raw transaction or TXID. Acceleration cannot help a transaction that was never broadcast or is not visible to the relevant service.
- Inspect its state. Check the confirmation count, fee rate in sat/vB, virtual size, mempool position, RBF status, unconfirmed parents, and whether a conflicting transaction spends the same inputs.
- Try the wallet’s fee bump first. If the sending wallet supports RBF and the transaction is eligible, use its built-in fee-bump option. Do not manually construct a replacement unless you understand inputs, outputs, change, signing, and wallet policy; a replacement usually has a different TXID.
- Check whether CPFP is possible. If you control a spendable unconfirmed output, see whether your wallet can create a child transaction with a sufficient fee. If an exchange controls the wallet or you do not control the relevant output, contact the exchange or sender instead.
- Consider an accelerator only after checking eligibility and terms. Confirm the transaction is visible and valid, RBF or CPFP is unavailable or impractical, and you are comfortable with the displayed cost and the possibility of no result. Read the service’s eligibility and refund terms before payment.
- Monitor the original TXID. Keep the request details and check the transaction independently afterward. Do not submit repeatedly unless the service permits it, and do not pay an unexplained second “release,” “unlock,” or “verification” charge.
Which option should you choose?
| Option | Best fit | Advantage | Limitation |
|---|---|---|---|
| Wallet RBF | You control the sending wallet and the transaction is replaceable. | Raises the on-chain fee through a replacement, without relying on an accelerator. | May be unavailable; the replacement changes the TXID. |
| Wallet CPFP | You control a spendable unconfirmed output. | Can raise the effective fee for a parent-and-child package. | Requires control of the relevant output and may cost more. |
| Fujn | The transaction is visible and wallet fee-bumping is unavailable or impractical. | TXID-based workflow with advertised free and paid routes. | Its performance and mining-pool claims are not independently audited; results depend on participation. |
| ViaBTC Accelerator | You want to submit directly to a mining-pool operator with published eligibility rules. | ViaBTC publishes free-route thresholds and failure conditions. | Free quotas, paid terms, transaction eligibility, and block timing can limit results; paid submission is described as non-refundable after submission. |
| Mempool Accelerator | You value published acceleration activity or need an out-of-band option. | Documents its model and publishes acceleration records. | Paid service with eligibility rules; rejected transactions and uncertain timing remain possible. |
| Wait | The fee is reasonable or congestion is easing. | No additional fee or third-party payment. | Confirmation time is uncertain. |
ViaBTC’s current rules and failure conditions are on its accelerator page and support page. Mempool explains its out-of-band model and payment methods at mempool.space/accelerator. Neither alternative guarantees a confirmation time.
Can Fujn be trusted?
Fujn is an accessible service at fujn.com, but the available information does not independently establish its reliability, success rate, mining-pool arrangements, or “leading” status. An active website is not proof that every performance claim is true, and a review score is not a measurement of confirmation success.
Trustpilot lists reviews for Fujn, but its listing includes a warning that Fujn displayed Trustpilot content incorrectly. Treat reviews as anecdotal reputation signals, not proof that an accelerator will confirm your transaction. See Fujn’s Trustpilot listing and the related Trustpilot page.
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- Use the official domain, not a search-ad result, social-media message, or lookalike site.
- Verify the payment address, amount, and network on the live service page; a crypto payment is generally irreversible.
- Do not pay a support agent’s personal address or an unexplained second fee to release an earlier payment.
- If a provider does not clearly explain eligibility, the fee, and its refund rules, do not send payment.
Why an acceleration request may not work
- The transaction cannot be found: The wallet may not have broadcast it, or the service’s nodes may not have received it. Resolve broadcast visibility before paying for acceleration.
- It has an unconfirmed parent: Accelerating a child alone may not help. ViaBTC lists unconfirmed previous transactions among reasons acceleration can fail.
- It conflicts with another spend: Two conflicting transactions cannot both be confirmed as valid spends. ViaBTC says double-spent transactions are unsupported.
- It exceeds free-route limits: Fujn and ViaBTC state a 0.5 KB limit for their free route. Larger transactions may be ineligible for that option.
- The fee is too low or no participating pool includes it: An out-of-band request does not change every miner’s policy or guarantee that a participating pool finds a block in time.
- It is already confirmed: Confirmed transactions cannot be accelerated. If a wallet or exchange has not credited the funds, check the TXID and contact that provider.
- You do not control the transaction: When an exchange created or holds the transaction, only that provider may be able to rebroadcast it or make a fee bump.
ViaBTC’s support guidance covers missing transactions, parent transactions, double-spends, and other failure conditions. If an exchange is involved, its support team is usually the right place to resolve a missing TXID or fee-bump request.
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