Glossary
What is a reduce-only order?
Also called: reduce only order, reduceOnly
Updated Ninja Terminal team
Definition
A reduce-only order is an order that can only reduce or close an existing position. It cannot open a new position or flip a long into a short. If the order would increase exposure, the exchange rejects or trims it. Traders use it on exits, take-profit orders, and stop-loss orders to avoid opening an unwanted position.
Without the flag, a sell order larger than your long position closes the long and opens a short with the remainder. Reduce-only prevents that.
When is it useful?
Example: you are long 1 BTC and have a resting limit sell for 1 BTC as a take-profit. You later close half manually. Without reduce-only, the resting sell for 1 BTC would still fill and leave you short 0.5 BTC. With reduce-only, it can only reduce the remaining 0.5 BTC.
It is standard on take-profit and stop-loss orders for this reason.
How do venues treat it?
| Venue | Behavior documented |
|---|---|
| Binance (USD-M) | reduceOnly parameter, default false. It cannot be sent in hedge mode, where the position side is used instead |
| OKX | reduceOnly applies to margin orders and to futures and swap orders in net mode only |
| Hyperliquid | A “Reduce Only” option: the order can only reduce a position, not open one in the opposite direction |
Bybit also supports a reduce-only flag on orders. Read your venue’s API notes for edge cases.
Where does it appear in Ninja Terminal?
Orders in Close mode are built to reduce a position, not to open a new one. On accounts in hedge mode, Ninja Terminal sends the position side instead of the reduce-only flag where the venue requires it. See the guide on hedge mode vs one-way mode.
Frequently asked questions
Can a reduce-only order increase my position?
No. If it would increase exposure or flip the position, the exchange rejects it or trims it, depending on its rules.
Why does Binance reject reduceOnly in hedge mode?
In hedge mode the position side already defines which leg an order reduces. Binance documents that reduceOnly cannot be sent there.