# Mempool

> The waiting area where pending transactions sit before they are included in a block.

Canonical URL: https://fudfomo.co/glossary/mempool
Source: What The Block! Dictionary v1.0 (last updated 2026-04-25), browsable at https://wtb.fudfomo.co.

## Definition

The mempool, short for memory pool, is a node's local list of pending transactions that have been broadcast but not yet included in a block. When the network is busy, the mempool grows and only the highest-fee transactions get picked up quickly.

The mempool is also the front-running playground: bots watch new transactions land in it and react in milliseconds. Some chains and rollups now offer private mempools to mitigate this.

## Related terms

- [Transaction](https://fudfomo.co/glossary/transaction): An instruction recorded on a blockchain that moves value or runs a smart contract.
- [Gas Fee](https://fudfomo.co/glossary/gas-fee): The cost of getting your transaction included on the blockchain. Goes to the people who run the network.
- [Front-Running](https://fudfomo.co/glossary/front-running): Profiting by placing your own transaction ahead of someone else's pending trade.
- [MEV](https://fudfomo.co/glossary/mev): Extra profit that validators or specialised bots can earn by reordering or inserting transactions in a block.

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