- Network congestion on the Bitcoin blockchain is the primary reason why some transactions remain pending for a period of time.
- Paying a higher Bitcoin transaction fee may help incentivize miners to process the trade.
- Human error is one of the key factors behind excessively long Bitcoin transaction times. Double-checking the receiving wallet address will mitigate this.
With only a set number of Bitcoin transactions allocated to each block of the Bitcoin blockchain, slow transaction speeds are common. However, if a transaction has not been confirmed for more than 24 hours it may be proactive to begin looking for other reasons. By understanding the top reasons why unconfirmed transactions may be stuck, it can be easier to remove trapped BTC from perpetuity.
Top Causes of Stuck Bitcoin Transactions
BTC transactions can remain pending for a host of different reasons. Below we have compiled some of the most common causes.
1. Congestion on the blockchain
Unfortunately, the Bitcoin blockchain has poor scalability. It can only handle a limited number of transactions per block. The average sits between 1,500 and 2,000. Imagine that the network is sent 100,000 transactions. If each block contained 2,000 transactions and a new block is added every 10 minutes - which is preprogrammed into the Bitcoin blockchain - it would take 8.3 hours for all transactions to get confirmed.
Finding the Bitcoin transaction ID and using blockchain explorers such as Blockchain.com and Blockstream can be useful to check the congestion of the network. If the average confirmation time is high, a stuck transaction may simply be the result of increased activity on the Bitcoin blockchain. However, if a transaction remains stuck beyond the average confirmation time, it may then be worth looking into other reasons.
2. Insufficient transaction fees
A fee must be paid with every bitcoin transaction. Transaction fees are automatically calculated by most crypto exchange platforms and are then attached to a transaction as an incentive for Bitcoin miners. However, a short spike in transaction fees may result in a transaction getting halted.
The average Bitcoin transaction fee is increased when there is a sudden influx of transactions into the network. If a transaction has been sent with a lower-than-average fee, bitcoin miners will not prioritize the pending transaction. Pending transactions remain within Bitcoin’s mempool - a memory pool where payments are organized and queued.
To incentivize Bitcoin miners to include the transaction users can either opt to pay additional fees or restart the payment. Restarting the payment should ensure that a higher fee is attached.
3. Inaccurate wallet address
A bitcoin transaction will remain stuck if an inaccurate recipient address is entered. Each bitcoin wallet is composed of a long string of both numbers and letters. Consequently, mistakes can occur when bitcoin wallet addresses are input. If one number or letter is out of sequence, the transaction cannot be confirmed because the network cannot identify which wallet address to send the payment to.
Those waiting for a stuck transaction should double-check to see if the correct recipient address was used. This can be verified from inside the bitcoin wallet used to initiate the transaction.
4. Transaction is too large for block size
Frustratingly, a transaction can get stuck in the Bitcoin blockchain if it is too large. Although rare, it is possible for the size of a transaction to be greater than Bitcoin’s block limit. The size of a transaction is dependent on the number of inputs and outputs. As the number of inputs and outputs increases, the size of the transaction expands. At a critical point, the size of a transaction may become too large to be processed by the blockchain.
While there are not many tools that can help to highlight the size of a bitcoin transaction there are logical steps that every person can take. If a transaction is not confirmed within 24 hours, and there is no other obvious reason why it has become stuck, it may be worth considering the complexity of the transaction.
Does the transaction involve multiple inputs and outputs? Is it more complex than sending a simple payment from A to B? If the answer is yes, it may have become stuck due to its size and may need to be reprocessed.
5. Internet failure
Although it is possible for the Bitcoin blockchain to operate without the Internet, the Internet makes things far simpler. That’s because the Internet is the best way to broadcast transactions to bitcoin miners within the network. Therefore, the processing of a transaction is heavily dependent on the reliability of an Internet connection.
If an Internet connection drops while a transaction is being broadcast, it may not reach all miners within the network. If it hasn’t reached all miners in the network then it will not be processed.
Fortunately, this is an easy fix. Before a transaction is sent, remember to check that an Internet connection is stable. This can be checked with Internet speed checkers such as fast.com or speedtest.net. If the problem of Internet connectivity persists, then evaluate the settings of any anti-virus software that may be installed on a device. A computer’s firewall can sometimes prevent data from being broadcast.
6. Problem with the recipient’s wallet
Sometimes a stuck transaction can have nothing to do with the sender and all to do with the recipient. If a transaction has been sent to a recipient but the recipient’s wallet address is not synchronized correctly with the Bitcoin blockchain, transactions can be halted. Wallet addresses that are not synchronized with the Bitcoin blockchain can be linked to restricted wallet accounts or inactive wallet providers.
To avoid problems with a recipient’s wallet address, reconfirm the wallet address with the person receiving the BTC payment. Ensure that the wallet is live and active. If a transaction has already been sent across the network, the transaction may need to be canceled.
7. Double spending
A double spend occurs when the same BTC is used for two separate transactions. It was one of the hardest challenges that the Bitcoin blockchain had to overcome when it was first launched. Thankfully, the problem of double spending is avoided through the validation process employed by Bitcoin miners.
However, at the wallet level, double spending can still technically occur. Most wallet providers digitally deduct the amount of BTC that has been committed to a single transaction. Therefore, the same BTC can’t be used for another transaction. However, some wallet providers may not implement this. In this scenario, theoretically, it might be possible to spend the same BTC on two separate transactions.
Although the double spent BTC will be caught by Bitcoin miners, there are no guarantees that it will be returned to a user's wallet. In this scenario, the best option would be to try to cancel the transaction by completing another double spend with a higher transaction fee.
8. Older Protocols
Since it was first launched in 2009, the Bitcoin blockchain has been updated multiple times. Alongside scalability, new protocols have helped to increase the blockchain’s functionality. Unfortunately, transactions cannot be processed across different protocol versions which means that some transactions can get stuck in the network.
For example, older Bitcoin architectures limited block sizes to 1MB. To improve scalability and speed up Bitcoin transaction times a protocol known as SegWit was introduced. However, after SegWit was introduced, it was the responsibility of each Bitcoin wallet provider to offer it as an option.
If a transaction has become stuck within the Bitcoin network and there is no other reason for the halt, check that both the sender and recipient’s wallet addresses are using the same protocol version. In the unfortunate scenario that a transaction has been sent to or from an older version of the Bitcoin protocol, the transaction will need to be canceled.
What Can I Do When My Transaction is Unconfirmed for Too Long?
There are several actions investors can perform if a Bitcoin transaction is taking longer than usual to process and send to the receiving wallet address. These include:
- Double-check that the recipient's wallet address is correct. A common issue for stuck transactions is an incorrect wallet address or blockchain network. Double-check to see if the correct recipient address was used. This can be verified from inside the bitcoin wallet used to initiate the transaction.
- Use a blockchain explorer to check the transaction status. All transactions need to be confirmed three times before a BTC payment is sent to a recipient. Check the number of approved confirmations by inputting a transaction ID into a Bitcoin block explorer.
- Wait at least 1 hour for the transaction to complete. If a transaction is stuck due to high congestion or low fees, it may just be a long waiting game. Wait at least 1 hour for the transaction to complete.
- Use the Replace by Fee method. Re-send the transaction with a higher fee. This will replace the original unconfirmed BTC transaction.
- Contact the exchange or wallet provider. Withdrawals from crypto exchanges and wallets can be halted for several reasons. For example, Binance withdrawals can fail due to scheduled maintenance, withdrawing above/below the required limit, and a negative account balance.
Can You Cancel Unconfirmed Bitcoin Transactions?
Yes, there are two prominent methods for canceling bitcoin transactions. These include the Replace By Fee (RBF) method and the Double Spend method.
To cancel an unconfirmed Bitcoin transaction, follow one of these methods:
- Resend the same transaction with a higher fee.
- Create a new transaction for the same amount but select a higher fee.
Replace By Fee Method
The Replace By Fee (RBF) protocol provides individuals with the option to resend a BTC transaction. The re-sent transaction has a higher fee and automatically replaces the original. In doing so, the unconfirmed transaction is removed and is no longer recorded.
It is important to note that only select bitcoin wallets are compatible with the RBF protocol. Those that are compatible will provide BTC holders with a check box before a transaction is sent. The option must be enabled for RBF to work.
Double Spend Method
If the RBF protocol is not available, or it has not been enabled, another option is to send a similar value transaction from the same wallet. The new transaction must be equal to the amount of the original and must be sent to yourself. This is completed using a higher transaction fee than the original.
As the process involves a double spend - the same BTC is spent twice - a specialized wallet or piece of software may be required. Once the second BTC transaction is sent, miners will prioritize the higher fee second transaction and remove the original. As the BTC is being to sent to you, the stuck BTC will be transferred back to the original wallet address.
Remember, transactions sent across the Bitcoin blockchain are meant to be irreversible. While both methods can help to ‘unstick’ a transaction, there is still a chance that they may not work.
Frequently Asked Questions
There is no exact length of time a BTC can remain stuck on the blockchain. If a transaction is not canceled, it can remain stuck until the cause is resolved. The uncertainty is also dependent on the Bitcoin blockchain processing times which can vary from 46 minutes to 6 hours. Therefore, it is impossible to know how long a transaction will take at any given time.
One of the best ways to speed up a stuck transaction is to increase the transaction fee associated with it. A higher transaction fee provides an increased incentive for Bitcoin miners which might be all that is required for the transaction to be completed. Many exchanges and wallet providers offer transaction accelerator services so, remember to check for these first.
Unconfirmed BTC transactions are very common and are usually nothing to worry about. It is accepted as part of the process of using the Bitcoin blockchain. However, if a transaction is unconfirmed for a long period of time, understanding the causes can help to relieve anxiety and find a solution.