Mempool
PROTOCOLDEFINITION
The waiting room for transactions: every broadcast payment sits in the mempool until a miner includes it in a block. Fuller mempool, higher fees.
There is no single mempool — each node keeps its own — but they converge on the same picture: a queue of unconfirmed transactions bidding for block space by fee rate (sats per vbyte). Miners take the highest bidders first.
Reading the mempool is a practical skill: send during a lull and pay a tenth of peak fees. Sites like mempool.space visualize the queue in real time — the fee ticker in our site header comes from exactly that data.
IN A SENTENCE
“The mempool cleared over the weekend, so she consolidated her UTXOs at two sats per vbyte.”
Key facts
Common questions
My transaction is stuck — what now?
It is waiting, not lost. Wait for congestion to ease, or bump the fee with RBF if your wallet supports it.
Can a mempool transaction be reversed?
Until confirmed it is not final — one reason merchants wait for at least one confirmation on meaningful amounts.