What Is MEV? Maximal Extractable Value Explained

MEV — Maximal Extractable Value — is one of the less visible but important forces in crypto. It's the extra profit that whoever orders transactions on a blockchain can squeeze out by choosing what goes first. If you've ever had a DEX trade fill at a worse price than expected, MEV may be why. This guide explains it in plain English.

What is MEV?

MEV stands for Maximal Extractable Value (originally 'Miner' Extractable Value). It's the value that can be captured by whoever decides the order of transactions in a block — typically validators or specialised parties working with them.

Here's the key fact that makes MEV possible: when you submit a transaction, it usually sits in a public waiting area (the 'mempool') before being confirmed. Anyone can see it. That visibility lets sophisticated players react to your transaction before it settles.

Common forms of MEV

MEV comes in several flavours. Some are harmless or even helpful to the market; others come directly out of ordinary users' pockets.

• Arbitrage — buying an asset cheaply on one DEX and selling it higher on another. Often beneficial, as it keeps prices aligned.
• Front-running — spotting your pending trade and placing the same trade just ahead of it to profit from the price move you're about to cause.
• Sandwich attacks — placing one order just before yours and one just after, so your trade fills at a worse price and the attacker pockets the difference.
• Liquidations — racing to be the one who closes out an under-collateralised DeFi loan and collects the reward.

Why MEV matters to you

For an everyday user, MEV usually shows up as worse-than-expected trade prices. A sandwich attack, for example, can quietly cost you a slice of every large or low-liquidity swap you make on a public DEX.

How to protect yourself

You can't eliminate MEV, but you can reduce how much it affects you.

• Set a tight slippage tolerance so a trade fails rather than filling at a bad price.
• Break large trades into smaller pieces to reduce the price impact attackers can exploit.
• Use MEV-protected transaction tools or private order routing where your exchange or wallet offers them.
• Trade more liquid pairs, where the spread an attacker can capture is smaller.

MEV is also being addressed at the protocol level. Various projects aim to make transaction ordering fairer or to share the resulting value more broadly, though this remains an active area of research.

Where to go next

MEV connects to several other core concepts. To understand who actually orders transactions, read about validators; to understand where MEV bites hardest, see what a DEX is and what DeFi is.

Frequently asked questions