How Does the “Fill or Kill” Order Type Mitigate Slippage Risk for Market Orders?

A "Fill or Kill" (FOK) order is a type of time-in-force instruction that requires the entire order to be executed immediately and completely, or it is cancelled. For a market order, FOK ensures that if the full quantity cannot be filled at the desired price or better, no partial execution occurs.

This prevents the order from being partially filled at increasingly worse prices deeper into the order book, thereby mitigating the risk of significant negative slippage.