What Is MEV (Maximal Extractable Value)?
MEV, or Maximal Extractable Value (originally "Miner Extractable Value"), is the maximum profit that can be gained by reordering, including, or excluding transactions within a block — beyond the standard block rewards and fees. Because block producers and specialized bots decide how transactions are ordered, they can arrange them in ways that capture extra value, often at ordinary users' expense.
MEV is a fundamental and much-discussed phenomenon in blockchains like Ethereum, with significant effects on fairness, fees, and user experience.
How Does MEV Work?
Pending transactions sit publicly in the mempool, visible before they're confirmed.
Bots scan the mempool for profitable opportunities (e.g. a large swap that will move a price).
They submit their own transactions and pay to influence ordering within the block.
By placing transactions before or after a target, they extract value.
Common Types of MEV
| Type | Description |
|---|---|
| Arbitrage | Profiting from price differences across DEXs |
| Front-running | Placing a trade ahead of a known pending trade |
| Back-running | Placing a trade right after a target transaction |
| Sandwich attack | Front- and back-running a trade to profit from its slippage |
| Liquidations | Racing to liquidate undercollateralized positions |
Why Does MEV Matter?
User cost — sandwich attacks and front-running can give users worse prices.
Higher fees — bots bidding for ordering can drive up gas costs.
Fairness — raises concerns about who benefits from transaction ordering.
Network health — influences blockchain design and decentralization debates.
How Users Can Reduce MEV Exposure
Set a sensible slippage tolerance to limit sandwich-attack profitability.
Use MEV-protected RPCs or private transaction services where available.
Avoid very large swaps in low-liquidity pools.
Consider limit orders rather than large market swaps in volatile conditions.
MEV and Trust Wallet
Trust Wallet gives you control over your trades, including the ability to adjust slippage tolerance on swaps — a key way to reduce vulnerability to MEV tactics like sandwich attacks. As a non-custodial wallet across 100+ blockchains, you decide how and when your transactions are made. Setting appropriate slippage and being mindful of trade size in low-liquidity pools helps protect you from unnecessary MEV losses.
