The Truth About WHAT IS BITCOIN MEMPOOL? In 3 Minutes

What Is Bitcoin Mempool?

As the name itself indicates, Mempool is nothing but a short form of “memory pool”. The mempool is the waiting or holding area for all the transactions that have been submitted yet not verified. Therefore, it is a collection of all Bitcoin transactions awaiting verification and confirmation by a Bitcoin miner which will be included in the next block.

Every node has some specific capacity for storing unconfirmed transactions. As a result, every node has its own version of the pending transactions depending on mempool size and transaction counts found in different sources.

Mempool Congestion

It may be caused by two reasons when:

  • Transaction volume is high

This reflects the number of transactions waiting to be confirmed on the blockchain is high, and simultaneously the volume of confirmations needed for processing is slow.

  • Trade hash decreases abruptly

It means that there are not enough miners to confirm each transaction.

How long does Bitcoin Transaction stay in a Mempool

The transactions residing in the mempool for over two weeks expire. By default, Bitcoin core nodes remove transactions from their mempool if no miner found transaction fees to be attractive enough to include them in a block over the last 336 hours (two weeks).

However, here are some tips that can be used to expedite transaction confirmation:

  • Use Replace By Fee (RBF): Some wallets like Electrum allow to replacement of an existing transaction with a new one with a higher fee.
  • Use transaction accelerators: Some mining pools supply a service of accelerating specific transactions for a fee or on a first come first serve basis.

Mempool Management

Now, the question is how do nodes keep from crashing due to the overload of pending transactions in the Mempool?

The answer is pretty normal that once the Mempool reaches its full capacity, the nodes start prioritizing transactions by setting up a minimal transaction fee threshold. Transactions with a fee rate lower than the threshold values are immediately removed from the Mempool and only new transactions with large enough fees are allowed access to the Mempool.

Importance of the Mempool

The Mempool is a part of Bitcoin Improvement Proposal No. 35 (BIP35). The thought was that outside nodes would be able to access other nodes’ Mempool.

This is useful for several instances:

  • SPV clients (also known as lite wallets) are willing to know about transactions before they were confirmed and entered into a block.
  • Miners who want to check for lucrative fees or download the current “transaction waiting list” in order to start confirming transactions.


The Mempool is a very important part of the Bitcoin network. The mempool analysis allows us to understand how crowded the network is and if there are “transaction traffic jams” which ultimately help us in calculating transaction fees. A high mempool size shows more network traffic causing a longer average confirmation time with a high transaction fee.

In a nutshell, Bitcoin transaction is somewhat complex but getting a raw transaction method to get raw transaction information makes it quite simpler and easy to understand.

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