What Is the Mempool?
The mempool (memory pool) is a waiting area where unconfirmed Bitcoin transactions are held before being included in a block. Each node maintains its own mempool, creating a distributed staging area for pending transactions across the network.
Waiting for Confirmation
When you broadcast a transaction, it enters the mempool of nodes across the network. Miners select transactions from their mempool to include in the next block, typically prioritizing those with higher fee rates.
How It Works
Transaction Priority
During high network activity, the mempool fills up with pending transactions. Those offering competitive fees get prioritized, while lower-fee transactions may wait longer or use RBF to speed up confirmation.
Fee Market
The mempool creates a dynamic fee market where users compete for block space. Monitoring mempool size and composition helps estimate appropriate fees for timely confirmation.
Each node's mempool may differ slightly due to network propagation delays and different relay policies. Transactions that don't confirm and lack sufficient fees may eventually be dropped from mempools, allowing the UTXOs to be spent again.
Quick Facts
- •Each node maintains its own mempool
- •Transactions sorted by fee rate
- •Size varies with network demand