What Is a Market Order in Crypto?

A market order says: do this trade now, at whatever the going price is. You choose the coin and the amount, the exchange matches you against whoever is already offering to trade, and it is done in a second. What you do not choose is the price. A market order guarantees that the trade happens; it does not guarantee what it happens at.

How does it fill?

Your order walks down the order book, the list of everyone waiting to buy and sell. It takes the best price first, then the next best, and keeps going until your amount is filled. For a small trade in a busy market that is invisible — you get almost exactly the price on the screen. For a large trade, or a quiet coin, you eat through the good prices and finish at worse ones. The difference between the price you expected and the price you got is called slippage, and it is the real cost of being in a hurry. Swapping a token on Uniswap works the same way: you take the price the pool offers at that instant, and a big swap moves it against you as it goes.

When is a market order the right tool?

When getting the trade done matters more than getting a good price. That covers most small everyday buys of Bitcoin or Ethereum on a major exchange, and it covers the moment you have decided to get out of something and do not want to negotiate. It is a bad tool in thin markets, during violent price moves, and for orders that are large compared with the coin's daily trading volume. Market orders also usually carry the higher of an exchange's two fees, because you are taking liquidity that someone else provided rather than adding your own.

How do you keep the cost down?

Check the buy and sell prices side by side before you press the button, since a wide gap is a warning that your order will be filled badly. Break a large order into several smaller ones. And if you have a price in mind rather than a deadline, use a limit order instead.

A simple habit that costs nothing: on any coin you have not traded before, send a small market order first and look at what you actually received. That one number tells you more about the market's real depth than any chart will.