On Kraken Futures, a limit order sets the price boundary, post-only controls whether the order may take liquidity immediately, and reduce-only limits the order to shrinking an existing position. These are separate controls: a trader can sometimes combine post-only and reduce-only for an exit that must rest on the book and must not increase exposure.
What each Kraken Futures order type controls
The three labels answer different questions about a futures order. Limit answers “What price am I willing to accept?” Post-only answers “May this order execute immediately, or must it become a maker order?” Reduce-only answers “Is this order allowed to change my position only by making it smaller?” Understanding those dimensions prevents common entry and exit mistakes.
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Limit orders: a price boundary
A limit order lets you specify the highest price you will pay for a buy or the lowest price you will accept for a sell. Kraken says that when there is not enough opposing demand or supply for immediate matching, the order is added to the order book.
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A limit order is not automatically maker-only. If your price reaches available orders on the opposite side, it may execute immediately as a taker. Kraken’s documentation also states that a limit order may be marked maker-only and/or reduce-only, so those controls should be treated as additional instructions rather than different price-order mechanics.
Post-only (maker-only): a liquidity rule
Kraken uses “maker-only” and “post-only” for the same execution intent. A post-only order is a limit order that must first rest on the book. Kraken states that it will be rejected or cancelled if the entered price would execute immediately.
For a buy, an order priced through the available asks would cross the spread and take liquidity. With post-only enabled, Kraken cancels or rejects that order instead of filling it. For a sell, the same protection applies if the price would match available bids immediately.
Post-only therefore changes the outcome of a crossing price, not the price limit itself. It does not promise that the order will fill, nor does it guarantee a particular fee. If the market moves away, the order can remain unfilled; if your price is already marketable, the order can disappear rather than trade.
Reduce-only: a position-size safeguard
Reduce-only is a position modifier. Kraken defines it as allowing only orders that reduce the number of open contracts in an existing position. It cannot open a new position or add to an existing one.
If you hold a long position, a reduce-only sell can close part or all of that long. It cannot sell beyond the amount needed to close the long and leave you short. If you hold a short position, a reduce-only buy can cover part or all of it, but cannot create a long position after the short is closed.
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When the requested quantity exceeds the open position, Kraken says the quantity is automatically reduced to the position size. This protection is especially useful when an exit order is left working while other orders, fills or manual actions may change the position.
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| Control | What it controls | If the price would cross the spread | Can it increase exposure? |
|---|---|---|---|
| Limit | The maximum buy price or minimum sell price | It may execute immediately if priced through the spread; otherwise it can rest | Yes, unless reduce-only is also selected |
| Post-only / maker-only | Whether the order may take liquidity immediately | Rejected or cancelled instead of executing immediately | Yes, unless reduce-only is also selected |
| Reduce-only | The effect on an existing position | It does not itself require maker execution; it constrains the resulting position | No; it can only reduce an existing position |
The practical distinction is that post-only describes the order’s interaction with the order book, while reduce-only describes its permitted effect on your position. One controls execution style; the other controls exposure.
How crossing the spread determines an immediate fill
The order book has bids from buyers and asks from sellers. The best bid is the highest currently posted buy price, and the best ask is the lowest currently posted sell price. The gap between them is the spread.
A buy limit below the best ask normally has to wait for a seller. A buy limit at or above an available ask can match immediately, depending on the book and matching rules. A sell limit above the best bid normally waits; a sell limit at or below an available bid can match immediately.
That distinction matters because a regular limit order may become a taker when it is marketable, whereas a post-only order refuses that immediate match. In a fast market, the book can change between submission and validation. An order that appeared non-crossing on your screen may be treated as immediately executable when Kraken processes it, causing a post-only cancellation.
Worked examples
Limit order used as an entry
Assume a futures contract shows a best bid of 50,000 and a best ask of 50,050. You want to enter long only at 49,900, so you submit a buy limit at 49,900. The order waits for a seller willing to trade at that price or better. It can remain open without any fill, and a later market move can leave it behind the current trading range.
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If instead you submit a buy limit at 50,100, the order is priced through the displayed ask and may fill immediately against available offers. It remains a limit order because the price caps what you will pay, but it is not necessarily maker-only.
Post-only entry
Using the same book, you submit a buy limit at 50,050 with post-only enabled. Because that price could match the ask immediately, Kraken rejects or cancels the order rather than allowing a taker fill. To post successfully, you would need a price that does not immediately match the available asks at the time of validation.
If another trader removes the best ask just before your order arrives, the result can differ. Post-only checks the live book, not the quote you saw several seconds earlier.
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Reduce-only exit from a long
Suppose you hold a long position of 3 contracts and place a reduce-only sell for 2 contracts. If filled, it can reduce the long to 1 contract. It cannot increase the long and cannot reverse you into a short.
If you accidentally request 5 contracts, Kraken says the quantity is automatically reduced to the size of the existing position. The order therefore cannot close more than the position available under the reduce-only rule. This does not mean the order will fill; price, liquidity and order status still determine execution.
Reduce-only exit from a short
With a short position of 4 contracts, a reduce-only buy for 1 contract can cover one contract and leave 3 short. A buy quantity larger than the open short is constrained to the position size rather than turning the remainder into a long position.
Post-only plus reduce-only
Consider a long position that you want to trim at a chosen price, but you do not want the exit to take liquidity or create a short position. A sell order with both post-only and reduce-only expresses those two requirements: it must rest as a maker order, and any fill may only reduce the long.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallThese are independent constraints. Post-only can cancel the order if the price crosses the book; reduce-only can limit quantity or prevent an exposure increase. A combined order can therefore be cancelled for being marketable, reduced in size because the position changed, or left unfilled while both conditions remain satisfied.
Can you use post-only and reduce-only together?
Conceptually, yes: the controls address different dimensions and Kraken documentation describes limit orders as capable of being maker-only and/or reduce-only. Whether the combination is available for a particular Futures instrument, interface control or API request must be confirmed in the current Kraken Futures interface and API reference before submission.
When the combination is supported, check the order after submission rather than assuming it is active. Verify that the order is open, that the displayed quantity reflects the current position, and that the order type shows the maker-only setting you intended. If the market crosses your price, a post-only instruction can cancel the order, leaving no protective exit in place.
A safe workflow for submitting an order
- Confirm the instrument and side. Check the exact Futures contract, whether you are buying or selling, and whether your current position is long, short or flat.
- Choose the price instruction. Enter the limit price that represents your maximum buy price or minimum sell price. Do not treat a limit price as a promise of execution.
- Decide whether maker-only behavior is required. Enable post-only or maker-only only when an immediate fill would be unacceptable. Expect cancellation if the entered price crosses the live book.
- Decide whether exposure must only decrease. Enable reduce-only for an exit or trim that must not open a new position. It is not an entry safeguard for a flat account because there is no existing position to reduce.
- Check quantity against the live position. For a reduce-only order, make sure the requested contracts match the portion you intend to close. Kraken may reduce an oversized request to the open-position size.
- Review the confirmation and status. Confirm the order type, price, quantity and modifiers before sending. After submission, look for an open, cancelled, rejected or filled status; a post-only cancellation means no position change occurred.
- Monitor competing exits. If another order or manual trade changes the position, reassess remaining reduce-only orders and their quantities. A working order may no longer represent the amount you intended to close.
Interface labels and supported combinations can change. Kraken’s current documentation and the live order ticket should take precedence over an older screenshot, saved workflow or third-party explanation.
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Kraken’s public Futures order-event schema includes separate orderType and reduceOnly fields. That separation mirrors the trading logic: one field identifies the order’s basic type, while the Boolean-style position modifier records whether it is reduce-only.
Documentation and tools may call post-only “maker-only.” Treat those labels as the same execution intention, but inspect the exact parameter names and accepted values in the current API reference when integrating software. A valid limit price does not by itself prove that post-only or reduce-only was transmitted.
For automated trading, handle rejection and cancellation as normal outcomes. A post-only order can be rejected because it would execute immediately; a reduce-only order can be resized when the position is smaller than requested. Your system should read the resulting order event and position state instead of assuming the original quantity remains active.
Common mistakes and how to correct them
Assuming every limit order is maker-only
A limit order can execute immediately when its price crosses the spread. If maker-only behavior is essential, select post-only and be prepared for rejection or cancellation.
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Using reduce-only as a guaranteed stop
Reduce-only restricts what a fill may do to the position; it does not guarantee a fill, a trigger, or a particular exit price. A resting reduce-only limit can remain open while the market moves away.
Expecting post-only to improve the price
Post-only does not move your limit to a better quote. It either rests at the submitted price or is rejected/cancelled when immediate execution would occur.
Leaving an oversized reduce-only order unattended
Although Kraken can reduce the requested quantity to the current position size, subsequent fills or other trades can change that position. Recheck open orders after partial exits or manual adjustments.
Confusing cancellation with a fill
A post-only cancellation is a non-execution event. If the order was meant to protect a position, decide whether to submit a new price that will rest, use a different order instruction, or accept that no exit is currently working.
Choosing the right combination
- Use a plain limit order when price control matters and an immediate fill is acceptable if the limit is marketable.
- Add post-only when the order must not take liquidity immediately and cancellation is preferable to a taker execution.
- Add reduce-only when the order is intended to close or trim an existing position and must not reverse or add exposure.
- Use both post-only and reduce-only for a planned resting exit when the current Kraken instrument and order interface support both modifiers.
Before relying on any combination in a live position, verify the current contract rules, order-ticket options and API behavior. Kraken notes that interface labels, fee schedules, supported combinations and regional rules can change; the live Futures product and current documentation are the authoritative checks.
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