What is MEV (Miner Extractable Value)?
Crypto Glossary Definition
MEV represents value that can be acquired from a block by re-ordering including, and excluding transactions. While transactions with the highest fees are typically always included in the next block, miners are not required to sort the transactions by highest paid fees. This allows them to reorder transactions to extract additional profits from users.
Why MEV (Miner Extractable Value) Matters
MEV is the profit miners or validators can extract by strategically ordering, including, or excluding transactions within a block — for example, spotting a large pending trade and placing their own trade just before and after it. It's an active area of research because it can effectively act as a hidden tax on regular users.
MEV (Miner Extractable Value) in Practice
A trader submits a large pending swap on a decentralized exchange, aiming to buy a sizeable amount of a token, which will predictably push its price up once executed. Before that transaction gets confirmed, a specialized bot monitoring the public mempool spots it sitting there, unconfirmed, and recognizes the profit opportunity. The bot quickly submits its own buy order with a higher gas fee, ensuring it gets processed first, then lets the original trader's large transaction go through right after — pushing the price up further, exactly as anticipated — and immediately sells into that price increase, pocketing the difference. This entire maneuver, known as a sandwich attack, is one of the most common forms of MEV, essentially value extracted from an ordinary user simply because their pending transaction was visible and predictable before it was confirmed. Miners and validators are positioned to extract this value directly since they control transaction ordering within a block, though today much of it flows through specialized searchers and builders competing to capture these opportunities and share proceeds with validators via arrangements like MEV-Boost on Ethereum. Because the ordinary trader in this example effectively pays a hidden extra cost through worse execution, MEV research has increasingly focused on mitigations like private transaction relays and fair-ordering protocols designed to close off this kind of exploitation.
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