What to Do if Your Bitcoin Transaction Gets "Stuck"
The number of transactions on the Bitcoin network has steadily increased over the years. This means more blocks are filling up. And as not all transactions can be included in the blockchain straight away, backlogs form in miners’ “mempools” (a sort of “transaction queue.”)
Miners typically pick the transactions that pay the most fees and include these in their blocks first. Transactions that include lower fees are “outbid” on the so called “fee market,” and remain in miners’ mempools until a new block is found. If the transaction is outbid again, it has to wait until the next block.
This can lead to a suboptimal user experience. Transactions with too low a fee can take hours or even days to confirm, and sometimes never confirm at all.
- Sender of the Bitcoin transaction: Replace-by-fee (RBF), and Child-pays-for-parent (CPFP)
- Recipient of the Bitcoin transaction: Child-pays-for-parent (CPFP)
Bitcoin transaction accelerators
Mining Pool Accelerators
A mining pool may offer a premium service in which they will prioritize a transaction, usually for a fee. The ability for that pool to get a transaction confirmed is limited to their ability to get a block confirmed -- and most pools have a tiny fraction of the hashrate. For example, if a pool has 10% of the hashrate, they mine about a block every 100 minutes (1 hour and 40 minutes), on average. If a pool has 5% of the hashrate, then they mine one block about every 200 minutes (3 hours and 20 minutes), on average.
- https://pushtx.btc.com: This service is provided by BTC.com in cooperation with several main mining pools. The fee was around 70 USD on December 20, 2017 and the transaction was confirmed within 3 hours. You can pay by BCH or country-specific methods and they estimate the fee based on the transaction size. They promise a chance of 75% for including transactions in the next block within one hour. Within 4 hours the chance is claimed to be at 98%. They guarantee that if the transaction isn’t confirmed in 12 hours, the fees will be fully refunded to your card within 10 ~ 15 days. This policy is not applicable to the transactions which are removed or double-spent during the acceleration process.
- ViaBTC - overloaded as of December 20, 2017. ViaBTC implemented this service to protest against the prior 1MB limitation of the Bitcoin network. ViaBTC gives priority to user-submitted transactions for the next mined blocks by the ViaBTC pool. The only requirement is the transaction must include a minimum fee of 0.0001BTC/KB.The free-to-use nature of the service may have made it widely popular as every hour, the number of transaction requested reaches its limit and it is common to be presented with the message “Submissions are beyond limit. Please try later.” on the top middle of the page. This means one must wait for the next block to try a new submission. After submitting a transaction, there is a wait for the next block to be mined by ViaBTC Pool.
- PushTX - Poolin provides a transaction accelerator service in cooperation with several leading mining pools. PushTX is a bitcoin transaction accelerator that allows you to get faster confirmations on your unconfirmed transaction.
Third Party Accelerators
There are additional services claiming to be able to "accelerate" a transaction. Their ability to get a transaction confirmed faster is limited to re-broadcasting your transaction, to help in the situation where that mining pool has dropped your transaction already. The Bitcoin Core client already does re-broadcast a "stuck" transaction periodically to peer nodes, though these services possibly may broadcast a transaction directly to known mining pool nodes. These services could also pay a mining pool to include your transaction, just as you could do that yourself.
It is likely these "transaction accelerators" that are not the mining pools themselves are not actually helping to get a transaction confirmed faster.