Miner Extractable Value (MEV)
In short: Miner Extractable Value (MEV), also known as Maximal or Max Extractable Value, is a measure of the profit a block producer can make by deciding which…
Miner Extractable Value (MEV), also known as Maximal or Max Extractable Value, is a measure of the profit a block producer can make by deciding which transactions to include in a block, which to exclude, and how to order them.
Why it matters
Transaction order matters most on DEXs and lending protocols, where the same trade can be worth more or less depending on what happens just before or after it. On proof-of-stake networks, validators propose blocks instead of miners, which is why the broader name is now common. Some MEV, such as arbitrage between pools, helps keep prices in line, while other forms, such as sandwich attacks, make ordinary users pay more.
Example
A user submits a large swap on a DEX with a loose slippage setting. A bot spots it waiting in the public mempool, places a buy order just before it and a sell order just after it. The user's trade executes at a worse price, and the bot keeps the difference. This is called a sandwich attack, a form of front-running, and a tighter slippage limit reduces how much can be taken.