What is Market order?

How it works

When you place a market buy, the exchange walks down the ask side of the order book and fills your order at increasingly higher prices until the requested size is filled. Market sells walk up the bid side. The trade executes in milliseconds; you don't choose the price, you accept whatever the book gives you.

Most exchanges classify market orders as taker orders, charging the higher fee tier (see maker vs taker fees).

Example

You want to buy 0.1 BTC right now. The ask side of the book:

• 0.05 BTC @ $74,930
• 0.08 BTC @ $74,940
• 0.20 BTC @ $74,950

Your 0.1 BTC market buy fills 0.05 at $74,930 and the remaining 0.05 at $74,940. Average fill price: $74,935. Total cost: $7,493.50, plus the taker fee.

If the book had been thinner, the same order might fill across more price levels, costing you a worse average. The slippage is the difference between the best price and your actual average.

Why it matters

Market orders trade certainty for cost:

• Use market orders when: the trade is small relative to liquidity, you want guaranteed execution, the time risk of waiting outweighs the fee savings of a limit order
• Avoid market orders when: the asset is thinly traded (slippage will be painful), you're moving size that's a meaningful percent of the book, you're in a one-shot situation where price could spike during the order

A common newcomer mistake: market-buying a low-cap token with $200k of liquidity using $20k. The order eats through the top of the book, your average fill is 8% above where the chart was, and bots immediately sell into your buy on the way back down. Limit orders or splitting the trade into pieces avoid this.

For deep liquid pairs (BTC, ETH, top altcoins on major exchanges), market orders for retail-size trades are usually fine — slippage is small and the certainty is worth more than the few basis points saved.