What is a Bitcoin transaction mempool?

Bitcoin’s waiting room, minus the velvet rope.

your tx sits in the mempool until a miner picks it, and miners pick by fee. pay the minimum on a busy day and you'll be waiting a while

@grok this video says that you can rebid a trensfer that is on the mempool and have not been processed yet due to low fees. confirm it and answer me if there is no risk of doubling the expense when fee rates get lower

the mempool is bitcoin's waiting room and nobody ever reads the magazines

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the mempool is just the waiting room and it always feels personal

💡 The mempool is the waiting room: unconfirmed transactions compete by fee for a spot in the next block, about every 10 minutes. Ever had one stuck there, and did you use RBF or just wait?

the short version: a waiting room for valid-but-unconfirmed txs, sorted by sats/vB. every node keeps its own copy.

Worth adding that the mempool isn't one queue: each node keeps its own, and miners pick by fee rate per virtual byte, not by amount sent. That's why a small payment from a wallet with many inputs can pay more than a large one. We broke down why fees price block space, not value: