Market Order

A market order is an instruction to buy or sell immediately at the best price currently available on the order book. It prioritizes speed and certainty of execution over price: you will almost always get filled, but you accept whatever prices the resting orders offer.

For example, if you market-buy 1 ETH when the best ask is $3,000 for 0.6 ETH and the next ask is $3,005 for 2 ETH, you buy 0.6 ETH at $3,000 and 0.4 ETH at $3,005, for an average price slightly above the quoted $3,000. That difference between the expected and actual fill price is called slippage.

Market orders are useful when getting in or out quickly matters more than saving a few basis points, such as exiting a position during fast-moving news. On thin markets, however, a large market order can "walk the book" and fill at dramatically worse prices. A common misconception is that the price shown on the ticker is the price you will get; a market order actually fills against the ask side (when buying) or bid side (when selling), which can differ meaningfully in illiquid pairs.