What Is the Bitcoin Mempool? A Beginner’s Guide

What Is the Bitcoin Mempool? A Beginner's Guide

The Bitcoin mempool plays a crucial role in the Bitcoin network. It's where unconfirmed transactions land before they are added to a block on the blockchain.

Read on to learn what the mempool is, how it works, and how you can fast-track Bitcoin transactions that have been lingering in the mempool.

What Is the Mempool?

Mempool is an abbreviation of the term "memory pool." It's a temporary holding space for unconfirmed transactions on the Bitcoin network. All transactions must go through the mempool pending validation and eventual inclusion in a published block.

It's easy to think of the Bitcoin mempool as one big storage area where all of the network's transactions go first. But that isn't so. Every Bitcoin node has its own mempool where BTC transactions await verification.

The number of pending transactions a node can hold is known as the mempool space, which can vary depending on the available memory.

Some nodes have large memories, allowing them to handle many simultaneous transactions, while other nodes have smaller capacities, reducing their ability to manage large batches of transactional data.

Each BTC mempool can hold a unique set of unconfirmed transactions that the node typically arranges according to fees.

The Role of the Mempool in the Bitcoin Network

With the basics of the mempool out of the way, let's move on to its role in the Bitcoin network.

The mempool exists as a type of security measure that helps ensure that only valid transactions are processed by the network.

By temporarily holding transactions, the mempool allows the node to check their validity by determining that only the correct signatures (cryptographic proofs) are involved and that the sender's wallet has enough funds to facilitate the exchange. This process eliminates the possibility of double-spending or fraud from either party.

The node allows transactions to move to the mining and confirmation stage only if they pass the check.

How Does the Bitcoin Mempool Work?

After you initiate a Bitcoin transaction, it undergoes several steps before reaching the receiver's wallet.

First, a node receives your unconfirmed transaction and queues it to check for its validity. If everything holds up, it'll send it to its mempool as a pending transaction.

The second stage involves miners picking the pending transactions. As a rule of thumb, miners prioritize transactions with higher fees so they can earn more fee income per block.

Miners then start creating the next blocks to include on the blockchain. They add the transactions that they'd picked into these blocks and confirm them. To complete the process, they broadcast the mined blocks over the network.

The nodes then receive the new block with the included transactions. They remove it from their mempool, marking its confirmation. The funds sent will then be reflected in the recipient's Bitcoin wallet, which typically takes about 20 minutes.

Why Do Transactions Get Stuck in the Mempool?

Sometimes, transactions may get stuck in the Bitcoin mempool longer than you would like. Here are two reasons why your transaction may take longer to leave the mempool.

Low Fees

Mining is a resource-intensive venture, so every miner will choose transactions that provide the highest returns. Thus, you increase the chances of your transaction confirming faster when you pay more for its confirmation.

Network Congestion

The state of the Bitcoin network could also hamper the speedy completion of your transaction. At peak times, the blockchain has so many unconfirmed transactions to handle and may experience bottlenecks. In such instances, the overstretched network will struggle to complete your transactions.

How to Accelerate Transactions Stuck in the Mempool

If you'd like to speed up your transactions, there are two main options you can use.

Replace by Fee (RBF)

You can use the Replace by Fee function on a supported wallet, setting a higher transaction fee to an existing translation to incentivize miners to prioritize it.

Before setting the new fee, check the mempool's status to ensure your new fee is above average. If confirmed, the old transaction is invalidated to prevent double-spending.

For the new replacement transaction to work, ensure you flag the payment as RBF-enabled and that the transactions have the same outputs since the funds are sent to the same addresses.

Child Pay for Parent (CPFP)

Using the Child Pays for Parent (CPFP) approach, you set up a new transaction (the child) with higher fees but the same outputs as the unconfirmed one (the parent).

The new fees will incentivize the miner to pick the child transaction, but they have to confirm it together with the parent. Unlike RBF, which is performed by the sender, CPFP relies on the recipient.

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FAQs

What is the mempool count in Bitcoin?

The mempool count is the number of transactions pending confirmation on the Bitcoin network. It can vary based on the speed at which miners confirm network transactions. A higher mempool count occurs when the network is congested, leading to delayed transactions.

How long does Bitcoin stay in mempool?

The average block time for the Bitcoin network is ten minutes. However, transactions may remain unconfirmed in the mempool for longer periods. Typically, if that exceeds 48 hours, the nodes may drop the transaction from the mempool, and the sender may re-broadcast it to the network.