In OneKey, different order types are designed for different trading goals. Some help you execute as quickly as possible, some help you control the execution price, and others help you split a larger order over price levels or over time.
This article explains the order types currently supported in OneKey, when they may be useful, and what to keep in mind before placing an order.
What are order types?
An order type determines how your order enters the market and under what conditions it will be executed.
OneKey currently supports the following order types:
Market Order
Limit Order
Stop Market Order
Stop Limit Order
Scale Order
TWAP Order
Market Order
A market order is designed to execute as quickly as possible at the best available market price.
Market orders are useful when your priority is speed rather than entering at an exact price. Because the order is matched against available liquidity in the market, the final execution price may differ from the price shown when you place the order. This difference is commonly called slippage.
When to use it:
When you want to open or close a position quickly
When execution speed matters more than exact price
When you can accept some price deviation in fast-moving markets
Example:
If the current price is around 100 USDT and you place a buy market order, OneKey will submit the order for immediate execution at the best available ask prices in the market. If the market moves quickly, your final average execution price may end up above 100 USDT.
Limit Order
A limit order lets you define the price you want. The order will only execute at your specified price or a better price.
Limit orders are useful when you want more control over execution price. However, they are not guaranteed to fill. If the market never reaches your limit price, the order may remain open without being executed.
When to use it:
When price matters more than speed
When you want to wait for a specific entry or exit level
When you do not need immediate execution
Example:
If the current price is 100 USDT and you place a buy limit order at 98 USDT, the order will only execute if the market falls to 98 USDT or lower. If the market stays above 98 USDT, the order will not fill.
Stop Market Order
A stop market order places a market order once the trigger price is reached.
This order type is commonly used when you want the market to react to a specific price level before executing. Because the order becomes a market order after it is triggered, it is generally better for fast execution, but the final execution price may differ from the trigger price.
When to use it:
When you want to exit quickly after a stop is triggered
When you want to enter after a breakout
When execution speed matters more than precise execution price
Example:
If the current price is 100 USDT and you set a buy stop market order with a trigger price of 105 USDT, OneKey will submit a buy market order once the market reaches 105 USDT.
Stop Limit Order
A stop limit order places a limit order once the trigger price is reached.
Compared with a stop market order, this gives you more control over the final execution price. However, execution is not guaranteed. If the market moves too quickly after the trigger is reached, the limit order may remain unfilled.
When to use it:
When you want a trigger-based order with more price control
When you can accept the risk of not being filled
When price precision matters more than execution speed
Example:
If the current price is 100 USDT and you set a buy stop limit order with a trigger price of 105 USDT and a limit price of 105.5 USDT, OneKey will place a buy limit order at 105.5 USDT once the trigger price is reached. If the market continues moving up too quickly, the order may not fill.
Scale Order
A scale order splits one larger order into multiple limit orders across a price range.
This can be useful when you want to build or reduce a position gradually at different price levels instead of placing one large order at a single price. Scale orders can help reduce market impact and make it easier to work into or out of a position more smoothly.
Because a scale order is made up of multiple limit orders, full execution is not guaranteed. Each part of the order will only fill if the market reaches the corresponding price level.
When to use it:
When you want to enter a position gradually across a price range
When you want to reduce a position in stages
When you want to avoid placing one large order at a single price
Example:
If you want to buy within a range of 95 to 100 USDT, you can create a scale order that splits your total order into multiple limit orders across that range. As the market moves through those prices, the orders may fill step by step.
Additional note:
If Reduce-only is enabled, a scale order can only reduce an existing opposite position. It cannot increase your exposure or open a new position in the opposite direction.
TWAP Order
TWAP stands for Time-Weighted Average Price. A TWAP order splits one larger order into smaller orders and executes them gradually over a selected period of time.
TWAP is useful when you want to avoid placing a large order all at once. Instead of focusing on immediate execution, it is designed to spread execution over time so the overall execution price stays closer to the average market price during that period.
When to use it:
When you want to enter or exit gradually over time
When your order size is large enough to affect the market
When you care more about smoother average execution than immediate fills
Example:
If you want to buy 10 ETH over 2 hours, a TWAP order can split that order into smaller executions over the selected time window. This may reduce market impact compared with placing the full order all at once.
Additional note:
If Reduce-only is enabled, a TWAP order can only reduce an existing opposite position. It cannot increase your exposure or open a new position in the opposite direction.
What is Reduce-only?
Reduce-only is not a separate order type. It is an order instruction that limits the order so it can only reduce an existing position.
When Reduce-only is enabled, the order will not increase your position size and will not reverse your position into a new one.
Common use cases:
Taking profit
Stopping loss
Scaling out of a position
Avoiding accidental reverse exposure
Example:
If you already hold a long position, a sell Reduce-only order can be used to reduce or close that position. If you do not have a matching position, or if the order size is larger than the position that can be reduced, the order may not execute as expected.
How to choose the right order type
You can choose based on your goal:
If you care most about speed, consider a market order or stop market order
If you care most about price control, consider a limit order or stop limit order
If you want to execute across a price range, consider a scale order
If you want to execute over time, consider a TWAP order
If you only want to reduce an existing position, use
Reduce-onlywhen available
Risks to keep in mind
No order type can guarantee immediate execution, exact pricing, and zero slippage at the same time.
In fast-moving or low-liquidity markets:
Market orders may experience slippage
Limit orders may not fill
Trigger orders may execute differently from what you expected after they are activated
Scale and TWAP orders may only fill partially
FAQ
Will a market order always fill immediately?
A market order is designed to execute as quickly as possible, but the final execution still depends on available market liquidity. In volatile conditions, the execution price may differ from the quoted price.
Why did my limit order not fill?
Your limit order may not have filled because the market never reached your limit price, or because there was not enough liquidity available at that price.
What is the difference between a stop market order and a stop limit order?
A stop market order becomes a market order after the trigger price is reached, so it is generally better for speed. A stop limit order becomes a limit order after the trigger price is reached, so it gives you more price control but may not fill.
What is the difference between a scale order and a TWAP order?
A scale order splits an order across different price levels. A TWAP order splits an order over time. Scale is price-based, while TWAP is time-based.
Will a scale order or TWAP order always fully execute?
Not necessarily. A scale order only fills when the market reaches each price level. A TWAP order depends on market conditions during the selected time window, so full execution is not guaranteed.
Why did my Reduce-only order fail?
A Reduce-only order may fail if you do not have a matching position to reduce, or if the order size is larger than the amount of the position that can be closed.
Which order type is best for beginners?
Many users start with market orders and limit orders first, then gradually move on to stop orders, scale orders, and TWAP orders once they are more familiar with how each order type works.