What Is the Mempool and How Does It Relate to Transaction Confirmation?

The mempool, short for memory pool, is a waiting area for unconfirmed transactions that have been broadcast to the network but not yet included in a block. Every full node maintains its own version of the mempool, storing transactions that it deems valid.

Miners select transactions from their mempool to construct a new block, prioritizing those with the highest fee rate. A transaction must be in a miner's mempool to have a chance of being confirmed.

If a transaction is dropped from all mempools, it will not be confirmed unless re-broadcast.