What is MEV?

The idea in one paragraph

Pending transactions are visible before they are confirmed. A party that can see your swap and decide the order of transactions can place their own trades around yours when that is profitable. That is MEV.

How a sandwich attack works

• You submit a buy with a generous slippage limit.
• An attacker buys the same token just before you, pushing the price up.
• Your buy fills at the worse price, pushing it up further.
• The attacker sells right after you at the higher price and keeps the difference. You received fewer tokens than the quote suggested.

Ways to reduce your exposure

• Keep slippage as tight as the market allows. The attacker can only take what your limit lets them.
• Avoid very large trades in thin pools, where one order is easy to sandwich.
• Where a chain or route offers protected submission of transactions, prefer it. Availability differs by chain.
• Check the quote and the final fill after the trade, so you can see how far they differed.

What no tool can promise

MEV is a property of how public blockchains order transactions. Settings and routing reduce the effect but cannot remove it, and no trading terminal can promise it will never affect a trade.