Glossary / Transactions & fees
Stuck transaction
Also known as Pending transaction.
- Definition
- A stuck transaction is one that has been broadcast and accepted by nodes but keeps missing blocks, because the fee it pays sits below what miners are currently taking.
Nothing is broken when a payment stalls this way, and nothing has been lost. Block space is an auction with about 4 million weight units for sale every ten minutes, and a bid that was competitive yesterday can be outbid for days. Your coins are still yours the entire time, sitting in an unspent output that has not moved.
How it works
A transaction gets stuck because of arithmetic, not error, and the arithmetic runs against every other transaction waiting at the same moment.
Each node keeps a mempool of valid transactions it has heard about and has not yet seen mined, capped at 300 megabytes of memory by default. Miners build blocks from the top of that pool by fee rate. If yours is below the line, it simply waits its turn, and the line moves according to demand you cannot see coming: an exchange rebalancing, a token launch, a rush of ordinal inscriptions.
Two thresholds decide how long the wait can be. When a mempool is full, the node evicts the lowest paying transactions and raises its own minimum acceptance floor above the default 1 satoshi per virtual byte, so a very cheap transaction can be dropped by most of the network without ever being mined. Separately, Bitcoin Core forgets any transaction that has sat unmined for 336 hours, which is 14 days. After that, the coins behave as though nothing was ever sent, and the wallet can spend them again.
Congestion is spiky rather than constant. On April 20, 2024 the halving block, number 840,000, collected 37.6 BTC in fees, more than ten times the block subsidy paid to the same miner, because a token protocol launched in the same block. Weeks of near empty blocks can follow an episode like that. This is why patience is often the correct and cheapest response.
Diagnosis takes one minute. Look up the transaction id on a block explorer, read the fee rate in sat/vB, and compare it against the current mempool. If the pending backlog clears at a rate above yours, you are waiting. If the backlog is empty and your transaction is still not mined, the likelier problem is that it never propagated, which happens with poorly connected wallets and with transactions that break relay policy.
Why this matters when you buy bitcoin
Buyers meet stuck transactions in three places, and the right answer is different in each.
Depositing to an exchange. Your deposit will credit when the exchange's confirmation threshold is met, and there is nothing to do but wait. Do not open a support ticket in the first hour, and never take up an offer to "resend" the deposit, since paying twice is a real way to lose money.
Withdrawing to your own wallet. The transaction was built by the exchange, so you cannot rewrite it. The exchange reviews on this site note which venues let you choose your own fee rate, and choosing a low one at a busy moment is the most common cause of a slow withdrawal. If you need the coins now, spend the incoming output with a high fee child transaction.
Sending from your own wallet. Here you have full control. Bump the fee with a replacement, or wait for the weekend, when fee rates commonly fall by an order of magnitude.
There is also a scam layer that exists purely because stuck transactions frighten people. Search for help and you will find "transaction accelerators" that ask for a payment to an address, "recovery specialists" who claim to unstick anything for a percentage, and support accounts that appear in your replies within minutes of a public complaint. No third party can move your transaction without either the keys that signed it or a mining pool relationship. Anyone who asks you to send bitcoin, connect a wallet, or share a seed phrase to fix a pending payment is stealing from you.
Reading a stalled 5 sat/vB withdrawal
Picture a withdrawal broadcast on a Tuesday evening at 5 sat/vB, at a moment when the mempool cleared at 4 sat/vB. By Wednesday morning a large backlog has built and nothing under 40 sat/vB is confirming.
Your first move is to check where you sit. An explorer will show a position in the queue, and often an estimate of how many blocks are ahead of you. If the backlog above your fee rate is a few megabytes, this resolves in hours. If it is tens of megabytes and still growing, it does not.
Your second move is a cost comparison, and it is usually decisive. Bumping a stalled 141 virtual byte transaction from 5 sat/vB to 40 sat/vB costs about 5,640 satoshis in total, and if that is a rounding error against the amount you are moving, pay it. If the withdrawal was 50,000 satoshis in the first place, spending 11 percent of it to arrive four hours sooner is a bad trade, and waiting is better.
Your third move is to do nothing else. Rebroadcasting the same transaction changes nothing, because the network already has it. Sending a second payment from the same wallet is worse, since many wallets will build it from the same unconfirmed change and chain the new payment behind the old one.
Stuck transaction vs a transaction awaiting its first confirmation
A transaction awaiting its first confirmation is behaving normally, and most of the payments people describe as stuck are exactly this. Blocks arrive roughly every ten minutes on average, but mining is a random search, so gaps of forty minutes or more occur regularly without anything being wrong. A competitively priced transaction that has been pending for twenty minutes is not stuck.
The distinction is the fee rate, not the clock. Compare what your transaction pays against what the last few blocks actually accepted at the bottom of their range. If your rate is above that floor, you are waiting for a block. If it is below, you are waiting for the market to come down to you, and that can take days or, in the worst case, never happen before the transaction expires from mempools.