Executing a trade or transaction in anticipation of a known pending order to gain advantage; in crypto, often via observing the public mempool.
Front-running exploits knowledge of incoming orders, placing a higher-fee or earlier transaction to execute first. On DEXs, this can extract value by buying before and selling after a victim’s trade.
A bot detects a large swap in the mempool and submits a higher-fee transaction to buy first, pushing the price up; it then sells into the victim’s order.
Common mitigations include higher slippage protection, randomized delays, private orderflow, and batch auctions; some chains support private transactions or commit-reveal schemes.
A user submits a trade through a private relay to avoid mempool exposure and sets a tight slippage limit to reduce sandwich risk.
All terms and definitions may update as the Cryptionary improves.