MEV (maximal extractable value)

MEV is the extra profit a block producer can make by choosing the order, inclusion, or exclusion of transactions in a block, beyond normal fees and rewards. It matters to readers because it quietly taxes ordinary trades: the price you see isn't always the price you get once someone reorders transactions around yours. A common example is a sandwich attack, where a bot spots your pending Uniswap swap, buys the same token right before it to push the price up, lets your trade execute at the worse price, then sells immediately after for a quick profit. Researchers have tracked well over $1 billion in extracted MEV on Ethereum since 2020. Tools like Flashbots try to make this process more transparent and less harmful to regular users.