The quick version. An order is an instruction to an exchange’s matching engine, and every type trades one kind of certainty for another. A market order buys certainty of execution and gives up certainty of price. A limit order does the opposite: your price or nothing. A stop is not really a third type at all, just a trigger that fires one of the first two once a level is reached.
An order is an instruction, not a wish
Behind the buttons on any trading screen sits a matching engine. It holds a queue of unfilled orders and pairs them off by fixed rules, usually best price first and, among orders at the same price, whoever arrived earliest.
When you place an order you are telling that engine what you will accept, and it has no opinion about whether your decision is sensible. Every order type is a different answer to one question: of price and execution, which are you willing to leave uncertain?
Market orders: fill now, price whatever it turns out to be
A market order says take the best available price until my quantity is filled. On a venue with real activity it will almost always execute, and it will execute immediately. That is the entire point of it.
What it does not do is promise a price. The number on screen is the best resting order at that instant, and it covers only the size sitting at that level. If your order is larger, the remainder fills against the next level, then the next, each a little worse.
Traders call that walking the book, and the gap between the price you saw and the average price you got is slippage. In a thin market the gap can be startling, because very little may be resting near the quote and a great deal of empty space may sit behind it. We unpack the mechanics in liquidity and slippage.
A market order also crosses the spread by definition, and on most venues it pays the higher taker fee for removing liquidity rather than adding it.
Safety: A market order in a thin or fast-moving book can fill materially away from the quoted price, and the difference is yours to absorb. Before sending one, look at how much size is actually resting near the quote for the amount you intend to trade. The quote is a price for someone else’s small order, not a price for yours.
Limit orders: your price or nothing
A limit order sets the worst price you will accept. A buy limit fills at your price or lower, a sell limit at your price or higher, and it can never fill worse than the number you typed. That is a genuine guarantee, not a tendency.
The cost of that guarantee is that it might not fill. It can sit unfilled while the market stays away from your level, it can fill only partly, and even when price touches your number you may be behind others who arrived first and get nothing.
Because a limit order usually rests in the book rather than removing something from it, most venues treat it as a maker order and charge less. That is a fee schedule, not a reward for being clever, and an order that never fills has consequences of its own.
Stop orders: a trigger, not a safety net
A stop order does nothing at all until the market reaches a level you nominate. It is dormant, invisible to the book, and holds no place in the queue. When the trigger condition is met, the venue submits an order on your behalf.
Which order it submits is the part people miss. A plain stop, sometimes labelled stop-market, becomes a market order. It will very likely execute, at whatever the book offers at that moment. If price moved quickly through your level, that can be a long way past it.
A stop-limit becomes a limit order instead. Now your price is protected but your execution is not, and the scenario where it fails to fill is exactly the violent move you set it for. Neither variant is a flaw. They are the same trade-off wearing a different hat.
One detail worth checking on any venue: what actually triggers the stop. Some use the last traded price there, others an index drawn from several venues. A brief wick on one thin book can fire a stop that a broader reference price would have ignored.
The settings wrapped around the order
Most venues let you attach conditions that change how long an order lives and how it may interact with the book. The names are fairly standard.
- Good til cancelled. The order rests until it fills or you remove it, though some venues expire it after a set period anyway.
- Immediate or cancel. Fill whatever is available right now and cancel the rest rather than leaving it resting.
- Fill or kill. Fill the entire quantity immediately or cancel it all, for when a partial fill would be worse than none.
- Post-only. Reject the order rather than let it take liquidity, keeping it on the maker side of the fee schedule.
None of these change the underlying trade-off. They control what happens to the part of your order that cannot be satisfied on your terms.
Choosing between them without kidding yourself
The honest way to pick is to ask which uncertainty you can live with in this specific situation. If not trading at all would be the worse outcome, you are describing a market order. If trading at a bad price would be the worse outcome, you are describing a limit order.
What no order type can do is create an edge. This is plumbing. It sets your execution cost and your failure mode, not whether the underlying decision was any good.
Venues also differ on minimum sizes, tick sizes and trigger references, and the only reliable source is the exchange’s own documentation. Reading a book properly is the companion skill, covered in how to read an order book and risk management for crypto traders.
Key takeaways
- Market orders guarantee execution, not price. Limit orders guarantee price, not execution. Nothing guarantees both.
- The quoted price covers only the size resting at that level, so larger orders fill across worse levels.
- A stop is only a trigger. A stop-market can fill well beyond your level; a stop-limit may not fill at all.
- Check which price source triggers a stop on your venue, as last-trade and index triggers behave differently.
- Order types set your cost and your failure mode, not whether a decision was any good.
Frequently asked questions
Why did my market order fill at a worse price than the one on screen?
Because the quoted price only covers the orders resting at that exact level. If your size is larger, the remainder is matched against the next levels down the book, each less favourable than the one before, and your fill is the average across all of them. Thin books and fast markets widen that gap considerably.
Does a stop-loss guarantee I get out at my level?
No, and this is worth being clear about. A stop only guarantees that an order is submitted once the trigger is reached. A stop-market then takes whatever price is available, which in a sharp move can be far from your level. A stop-limit protects your price but may leave you unfilled. Neither is insurance.
Are limit orders always cheaper than market orders?
Usually the fee is lower, because resting orders add liquidity and most venues price maker fills below taker fills. That is neither universal nor the whole cost. An unfilled limit order carries the cost of the trade you did not make, which appears on no fee schedule but is real all the same.
What is the difference between a stop-limit and an ordinary limit order?
An ordinary limit order enters the book immediately and is visible to everyone. A stop-limit sits dormant until its trigger price is reached, at which point it submits a limit order. The difference is timing and visibility rather than the eventual instruction, which in both cases is fill at my price or better, or not at all.
Educational content, not financial advice. Crypto is volatile and high-risk; never share your seed phrase or private keys with anyone. Always do your own research.
Last updated Jul 25, 2026
