In simple terms — Pending transactions do not always have a final order. Whoever helps build a block can choose which transactions to include and in what sequence; the economic value obtainable from that choice is called MEV.
Today, MEV stands for maximal extractable value. The M originally meant miner, but the term was broadened because proof-of-stake networks and block- building markets involve validators, builders, and other participants. MEV is measured beyond the protocol's ordinary rewards and fees.
Searchers, builders, and execution order
Searchers watch blockchain state and look for profitable transaction sequences. They may submit transactions with competitive fees or ordered bundles to a builder. The block producer ultimately decides what to include under the network's and block-building market's architecture.
Common examples include arbitrage between pools, liquidation of undercollateralized loans, and a sandwich attack. Arbitrage and liquidation can realign prices or close risky debt, so not all MEV is equivalent to fraud. Some strategies, however, directly worsen a user's execution or increase congestion.
Effects and limits of observation
A transaction visible in the public mempool may reveal its limit price, quantity, and slippage tolerance. This information lets others try to execute before or after it. Failed transactions and priority bids can also become a collective cost.
MEV cannot be established merely by seeing an address make a profit. Analysis must reconstruct the block, transfers, alternative prices, and relationships among several actors. Ordering also does not always depend on one validator. Batch auctions, encrypted mempools, and private submission can reduce some forms of exposure, but they introduce other intermediaries and do not remove every extraction opportunity.
Sources
- Ethereum.org — Maximal extractable value — Defines MEV, its participants, strategies, and effects on the Ethereum ecosystem.
- Flash Boys 2.0 — A primary study of transaction ordering and front-running dynamics on decentralized exchanges.
Related entries
Sandwich attack · Flash loan · Front-running · Liquidity pool