Mempool Meaning & Definition

Key Takeaways

  • Mempool stands for 'Memory Pool'.
  • Mempools hold unconfirmed transactions in the Bitcoin network.
  • Size and congestion of the mempool can affect transaction fees and times.


The Mempool, short for “Memory Pool”, represents a collection of unconfirmed transactions in the Bitcoin network.

Each node maintains its own version of the mempool.

When a user broadcasts a Bitcoin transaction, it first gets verified by the nodes and then is held in the mempool until a miner picks it up and includes it in the next block.

This mechanism exists to hold transactions until they can be processed.

Given the decentralized nature of the Bitcoin network and the 10-minute average block time, there’s a need to manage transactions that wait for confirmation. The mempool handles this.

How Does Mempool Affect Fees?

When a user sends a Bitcoin transaction, they can choose to set a higher fee to incentivize miners to prioritize their transaction, leading to faster confirmation times.

Conversely, setting a lower fee might mean that the transaction takes longer to confirm, especially during times of mempool congestion.

  • High Mempool Size: Typically means higher transaction fees.
  • Low Mempool Size: Usually allows for lower transaction fees.

Understanding the current state of the mempool can help users make decisions about the amount of fees they’re going to pay for transactions.

Benefits and Limitations of Mempool


  • Allows the network to manage transaction overflow.
  • Provides flexibility for users in choosing transaction fees.
  • Maintains decentralization by ensuring every node can have its own mempool.


  • Mempool congestion can lead to slow transaction confirmations.
  • Users might have to pay higher fees during peak times.

Mempool Congestion

As the popularity of Bitcoin has grown, so has the number of transactions. There are times when there are more transactions than the network can process quickly, leading to what is known as mempool congestion.

When there is congestion:

  • Transactions might take longer to be confirmed.
  • Fees might increase as users compete to have their transactions processed faster.

A clear view of the mempool’s size and the number of unconfirmed transactions can provide insights into the state of the network.

Article Sources

BuyBitcoinWorldWide writers are subject-matter experts and base their articles on firsthand information, like interviews with experts, white papers or original studies and experience. We also use trusted research and studies from other well-known sources. You can learn more about our editorial guidelines.

  1. Binance Academy- Mempool,

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