Maximal extractable value, or MEV, arises because transaction order can change financial outcomes. A trade can move a pool's price, and an oracle update can make a loan eligible for liquidation. Whoever identifies and secures a favorable position in that sequence may capture value.
Who participates
MEV was originally called miner extractable value in proof-of-work settings. The broader name also covers proof-of-stake and other execution arrangements. Ethereum now uses proof-of-stake, so its MEV is not dependent on miners.
Searchers identify opportunities and submit transactions or bundles. Builders can assemble blocks, while validators propose them; these roles may interact through auctions and relays. Payments for inclusion distribute part of the opportunity's value across participants. A searcher's gross trading gain therefore differs from profit after execution costs and payments.
Useful incentives and harmful ordering
Arbitrage can align prices across markets, and liquidation incentives can help lending protocols manage unhealthy debt. Sandwich trading, however, can worsen another user's execution by placing trades before and after it.
MEV can also encourage costly competition and concentration in transaction infrastructure. Private submission and alternative trading designs can reduce some exposures, but their protection depends on implementation and trust assumptions. MEV is a category of ordering-related value, not a synonym for every blockchain exploit.