🔍 Introduction: What Is a FOK Order?
A FOK (Fill-or-Kill) order is a type of order that requires the entire order to be filled immediately. If the exchange cannot fill the full quantity of the order at the time it is placed, the entire order is canceled. No partial fills are allowed.
FOK orders are used by traders who require the exact order size and do not want to be left with a partial position. They are particularly useful for large orders, when you need to ensure you get the full position size, or when you are testing the market depth.
FOK orders are "all-or-none" — either the full order fills immediately, or it is completely canceled. There is no partial execution.
⚙️ How a FOK Order Works
When you place a FOK order, the exchange attempts to fill the entire quantity immediately at the best available price (or within your limit price). If the full quantity is available, the order fills completely. If not, the order is immediately canceled.
Example: You place a FOK order to buy 10 BTC at a limit price of $60,100. The order book has:
- 5 BTC available at $60,000
- 3 BTC available at $60,010
- 2 BTC available at $60,020
Since the total available liquidity within your limit price is 10 BTC, the full order fills. If only 9 BTC were available, the entire order would be canceled.
FOK orders can be placed as either limit FOK (with a limit price) or market FOK (executed at the best available price, but only if the full quantity is available).
Use a limit FOK order if you want to control the maximum price you're willing to pay (for buys) or the minimum price you'll accept (for sells) while still requiring a full fill.
✅ When to Use a FOK Order
FOK orders are ideal in the following scenarios:
When you need the exact order size and cannot accept a partial position.
FOK orders are useful for testing whether the market has enough liquidity to fill a large order.
Institutional traders often use FOK orders to execute large block trades without leaving a market footprint.
If you don't want to hold a partial position, FOK ensures you either get the full fill or nothing.
Use FOK orders when you are executing a strategy that requires a specific position size, such as hedging or portfolio rebalancing.
⚖️ FOK vs. IOC (Immediate-or-Cancel)
FOK and IOC orders are often compared. Here's the key difference:
| Feature | FOK | IOC |
|---|---|---|
| Definition | Fill-or-Kill | Immediate-or-Cancel |
| Partial Fill | Not allowed (all-or-none) | Allowed (unfilled portion canceled) |
| Order Cancellation | Entire order canceled if not fully filled | Only unfilled portion canceled |
| Best For | Requiring exact order size | Testing liquidity, partial execution acceptable |
| Price Control | Yes (if limit FOK) | Yes (if limit IOC) |
Choose FOK if you require the exact order size. Choose IOC if you are okay with a partial fill and want the rest canceled.
⚖️ FOK vs. Market vs. Limit Orders
Understanding the differences between these order types is essential:
| Feature | FOK | Market | Limit |
|---|---|---|---|
| Execution | Immediate (all-or-none) | Immediate | When limit price is reached |
| Partial Fill | Not allowed | Allowed | Allowed |
| Unfilled Portion | Canceled (if not fully filled) | Remains (partial fill possible) | Remains in order book |
| Price Control | Yes (with limit FOK) | No | Yes |
| Best For | Full fill requirement | Urgent trades | Price control & saving fees |
Use FOK when you need the exact order size. Use market orders for urgency, and limit orders for price control and lower fees.
⚠️ Risks of Using FOK Orders
While FOK orders are useful, they come with some risks:
- Order Cancellation: Your order may be entirely canceled if there is not enough liquidity to fill the full quantity, causing you to miss the opportunity.
- Worse Average Price: If the order fills, it may fill at multiple price levels, resulting in a higher average price (for buys) or lower average price (for sells).
- Not Suitable for Thin Markets: In low-liquidity markets, FOK orders are likely to be canceled.
- May Not Fill in Fast Markets: In rapidly moving markets, the available liquidity may change quickly, causing your FOK order to be canceled.
You place a FOK order to buy 10 BTC at a limit price of $60,100. Only 8 BTC are available at your limit price. Your order is entirely canceled, and you miss the opportunity to buy the 8 BTC.
📝 How to Set Up a FOK Order
Follow these steps to place a FOK order on most exchanges:
-
1
Choose your trading pair
Select the asset you want to trade (e.g., BTC/USDT).
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2
Select order type
In the order entry panel, choose "FOK" or "Fill-or-Kill" as the order type.
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3
Set your limit price (optional)
If using a limit FOK, enter the maximum price you're willing to pay (buy) or the minimum price you'll accept (sell).
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4
Enter the amount
Specify the quantity you want to trade.
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5
Review and place the order
Double-check your settings and click "Buy" or "Sell" to place the FOK order.
If you are using FOK with a limit price, ensure your limit price is realistic and there is sufficient liquidity at that level to fill your order.
✅ Best Practices for FOK Orders
- Check order book depth: Before placing a FOK order, check the order book to estimate whether your full order can be filled.
- Use limit FOK for price control: If you care about the price, use a limit FOK order to cap your execution price.
- Avoid FOK during low liquidity: In low-liquidity markets, FOK orders are likely to be canceled.
- Monitor order status: If your FOK order is canceled, decide whether to place a new order or adjust your strategy.
- Combine with other orders: If a FOK order is canceled, consider placing a limit order for the remaining amount.
FOK orders are powerful tools for requiring exact order sizes. Use them wisely, and always consider the trade-off between full execution and the risk of cancellation.