Maximal Extractable Value (MEV) — formerly Miner Extractable Value — refers to the profit that block producers (miners in PoW, validators in PoS) can extract from users by controlling the ordering of transactions within a block. MEV represents a hidden tax on blockchain users and has become one of the most analysed and debated aspects of DeFi economics. HOW MEV ARISES Every pending blockchain transaction sits in the public mempool awaiting inclusion in a block. Whoever produces the next block (miner or validator) can: include transactions in any order, exclude specific transactions entirely, and insert their own transactions anywhere in the sequence. This ordering power creates opportunities to profit at users' expense. COMMON MEV EXTRACTION STRATEGIES Sandwich Attacks: The most common form targeting DEX swaps. MEV bot detects a large DEX swap in the mempool. Bot front-runs the victim: submits a buy order with higher gas to execute just before the victim's swap — pushing the price up. Victim's swap executes at the artificially elevated price. Bot back-runs: sells immediately after the victim's swap — profiting from the price movement it created. The victim receives fewer tokens than expected. Arbitrage: MEV bots detect price differences between DEXs and execute profitable arbitrage. This is generally considered beneficial MEV — it improves market efficiency and doesn't harm users. Liquidation Racing: When a DeFi loan becomes undercollateralised, a liquidation becomes profitable. MEV bots race to be the first to execute the liquidation and claim the bonus. THE FLASHBOTS RESPONSE Flashbots is a research organisation that built MEV-Boost — infrastructure allowing validators to receive MEV-optimised blocks from specialised "block builders." MEV-Boost has captured most Ethereum block production, creating a transparent marketplace for MEV rather than chaotic mempool warfare. Flashbots Protect RPC allows users to submit transactions privately — hidden from public MEV bots. Over 90% of Ethereum validators use MEV-Boost.