What Is a Market Order?
A market order is an instruction to buy or sell an asset immediately at the best price currently available in the order book. Market buy orders execute at the ask price; market sell orders execute at the bid price. You get guaranteed execution but no price guarantee.
How Market Orders Work
When you place a market buy, your order is matched against the lowest-priced sell orders in the book. For small orders in liquid markets, you'll get the displayed ask price. For large orders or in thin markets, your order may "walk the book," filling across multiple price levels and experiencing slippage — each subsequent fill at a worse price.
Why It Matters for Traders
Market orders are essential when you need immediate execution — entering volatile breakouts, emergency exits, or reacting to news. However, the slippage cost can be significant. Professional traders use limit orders for planned entries and reserve market orders for urgent execution, always checking order book depth before placing large market orders.