GlossaryWhat is MEV?
What is MEV?
MEV, short for maximal extractable value, is the extra value that can be taken from producing a block by choosing which transactions go in, which stay out and in what order. ethereum.org counts it as value beyond the normal block reward and gas fees, and it shows up whenever a pending trade moves a price.
What MEV Means in Crypto
MEV in crypto means the profit someone can make from controlling transaction order inside a block. The term began as miner extractable value, and ethereum.org says it was renamed maximal extractable value after The Merge moved block production from miners to validators, as explained on ethereum.org's MEV page.
Transactions wait in a public queue, the mempool, before they land in a block. Anyone watching that queue can see a big trade coming and try to place their own transaction right before or after it. The block producer decides the final order, so the value of that position flows toward whoever builds the block.
Who Extracts MEV
Searchers extract most MEV: they are independent operators running bots that scan for profitable orderings. ethereum.org notes that validators could in theory take all of it, but in practice searchers find the trades and then bid high gas fees to get them included.
That bidding hands much of the profit to validators anyway. For crowded trades such as DEX arbitrage, ethereum.org says searchers may pay 90% or more of their MEV as fees.1 Ethereum gas sits at 0.06 gwei at this check.
Common Types of MEV
The common types of MEV are arbitrage, liquidations and sandwich trades, and ethereum.org treats the first two as useful to markets.
- DEX arbitrage: buying a token where it is cheap and selling where it is dearer in one transaction. ethereum.org cites a searcher who turned 1,000 ETH into 1,045 ETH from an ETH/DAI gap between Uniswap and Sushiswap.
- Liquidations: lending protocols let anyone close an undercollateralized loan for a fee, so bots race to be first.
- Sandwich trades: a bot places one trade before a large swap and one after it, covered in the next section.
Arbitrage keeps prices on a decentralized exchange in line with the rest of the market, and quick liquidations protect lenders.
How a Sandwich Attack Works
A sandwich attack works by wrapping a victim's swap between two of the attacker's own trades. The bot spots a large pending swap, buys the same token first so the price rises, lets the victim's trade fill at that worse price, then sells right after. ethereum.org calls the first leg a front-run and the second a back-run.
The victim pays for it through extra slippage: the trade still goes through, just at a worse rate than it would have. ethereum.org lists this worse execution as a direct harm of MEV for ordinary users.
Flashbots and MEV-Boost
Flashbots, the group behind MEV-Boost, is a research and development organization that works to reduce the harm MEV causes, starting with Ethereum, according to the Flashbots docs. MEV-Boost is open source software validators run to buy finished blocks from a market of specialist builders.3
Builders assemble full blocks and send them to relays, and relays pass the most profitable block to the validator. ethereum.org calls this split proposer-builder separation. Flashbots also runs Flashbots Protect, which sends a transaction to a private mempool out of view of sandwich bots and only includes it if it does not revert.4
Why MEV Worries Ethereum Developers
MEV worries Ethereum developers because it can push up fees and pull block production toward a few large players. ethereum.org lists gas wars that congest the network, the risk that MEV larger than the block reward tempts validators to reorganize blocks, and the edge large staking pools have over solo stakers.
MEV is not limited to Ethereum. On Solana, Jito says its liquid staking token passes MEV rewards to stakers on top of normal staking rewards, which the liquid staking page covers.
Questions People Ask About What is MEV
These are the questions people ask next about what is mev.
What does MEV stand for?
MEV stands for maximal extractable value. It was first called miner extractable value, and ethereum.org says the name changed after The Merge, when validators replaced miners as the ones producing Ethereum blocks.
Is MEV bad?
MEV is not all bad, according to ethereum.org: it comes from how public blockchains order transactions, and ethereum.org describes arbitrage and liquidations as useful to markets. Sandwich trading is the form ethereum.org flags as harmful to users, because it worsens the price they get.
How can I avoid a sandwich attack?
A sandwich attack needs to see your swap before it lands, so routing it privately helps. Flashbots Protect sends transactions to a private mempool hidden from frontrunning and sandwich bots. Setting a tight slippage limit also caps how much worse your fill can get.
What is an MEV bot?
An MEV bot is software a searcher runs to scan pending transactions and blocks for profitable orderings, such as arbitrage, liquidations or sandwich trades, and then submit transactions that capture them, often with a high fee to win a place in the block.
Sources
Every number on this page comes from these sources, checked November 9, 2026.