Market order
TradingUpdated 11.08.20261 min
A market order buys or sells immediately at the best available prices. It almost always fills and fills at once, but the price comes from the book rather than from you: on a thin pair it lands worse than the screen showed.
How it works
The order walks the book, taking counter-offers in turn until the size is filled. If the best price holds less than you need, the remainder fills at worse ones, and your real price is the average.
So the cost of a market order depends not on size in itself but on size relative to the book's depth. The same amount on bitcoin and on a small altcoin are entirely different stories.
Exchanges usually charge more for market orders: they take liquidity out of the book rather than adding it.
When it is the right tool
- When filling matters more than priceExiting into a fall or an urgent purchase: cases where not trading costs more than the slippage.
- On a liquid pair in modest sizeSwapping a couple of hundred dollars in BTC/USDT, the difference from a limit order is measured in cents.
- Not for thin pairsOn an illiquid altcoin a market order can move the price by whole percent with your trade alone.
- Read the book before sendingDepth is visible in advance. Estimating slippage takes seconds and costs less than discovering it afterwards.