Maximal Extractable Value (MEV)
Profit that block producers can capture by choosing how to order or insert transactions within the blocks they build.
When a profitable trade sits in the public mempool, whoever builds the next block can act on it. They might place their own buy just ahead of a large order, then sell into the price it moves, a sandwich attack. Liquidations and arbitrage are also harvested this way. Estimates put cumulative MEV on Ethereum in the billions of dollars.
The original term was miner extractable value; it became maximal after the move to proof-of-stake. MEV is not purely parasitic, since arbitrage keeps prices aligned across venues. But the worst forms tax ordinary users. Tools like Flashbots try to make the market for block space more orderly.
Related terms
Profiting by seeing a pending transaction and pushing your own ahead of it for guaranteed gain.
MempoolThe waiting room where broadcast transactions sit before a miner or validator picks them for a block.
SequencerThe rollup component that decides the order of incoming transactions and posts them as compressed batches to the base chain.
ArbitrageProfiting from the same asset trading at different prices in two places by buying low and selling high.