Mempool
A mempool is a node's temporary pool of valid, unconfirmed transactions waiting to be included in a block.
✦ Key Insight
Mempools explain why transactions can remain pending, be replaced, or be observed before confirmation. Publicly visible pending transactions can also create opportunities for front-running and other MEV strategies.
✕ Common Misconceptions
There is no single universal mempool shared identically by every node. Private order flow, local policies, propagation delays, and alternative account-abstraction mempools can change what different participants see.
Detailed Explanation
In Practice
Dig Deeper
Confirmation
A confirmation indicates that a transaction has been included in a block and has gained additional blockchain history after it.
Transaction
A blockchain transaction is a signed or authorized instruction that changes blockchain state or transfers value when accepted by the network.
Nonce (account)
An account nonce is a sequence value used to order transactions from an account and help prevent the same signed transaction from being replayed repeatedly.
MEV
MEV is value that can be extracted by strategically including, excluding, or ordering transactions around normal blockchain activity.
Gas Fee
A gas fee is the network fee paid for computation and transaction execution on blockchains that use a gas-based fee model.