Advanced Limit Orders in Crypto Trading: Post Only, FOK & IOC Explained

Compared to standard limit orders, advanced limit orders provide three additional execution mechanisms: Post Only, Fill or Kill (FOK), and Immediate or Cancel (IOC). By contrast, regular limit orders default to the Good Till Cancelled (GTC) mechanism.

Advanced limit orders are particularly useful for market makers and day traders, especially those dealing with smaller, less liquid cryptocurrencies.

Post Only

Post Only is the default mode for advanced limit orders. It ensures that your order is always added to the order book as a maker order i.e. earning maker fee discounts，without executing immediately.

If the system detects that a Post Only order would match an existing order upon submission, it will automatically cancel the order to preserve your maker status.

Because crypto markets typically have lower liquidity compared to traditional finance, Post Only mode is widely used by quantitative trading firms and exchange market makers. By providing liquidity rather than consuming it, traders gain a strategic advantage.

⚠️ Note: Post Only is still a type of limit order. Like all limit orders, it does not guarantee execution.

 

Fill or Kill (FOK)

A Fill or Kill order must be entirely filled immediately upon reaching the order book; otherwise, it is canceled in full.

FOK is designed for professional traders. While not commonly used by casual users, it is popular among day traders—particularly those employing scalping strategies. For these traders, partial fills often reduce profit margins to the point where the trade is no longer worthwhile.

FOK is especially effective in:

• Low-liquidity markets (e.g., small-cap cryptocurrencies).
  
  
• Options and futures trading, where spreads need to be captured in full.
  
  

In essence, a FOK order sends a clear message to the market: “This is my price. Either fill it completely, or don’t fill it at all.”

Immediate or Cancel (IOC)

An Immediate or Cancel order is similar to FOK but allows partial fills. Any unfilled portion of the order is immediately canceled.

IOC is often used by short-term traders looking to capture quick profits from small price fluctuations. These traders typically submit a high volume of orders where speed and partial execution are acceptable.

IOC orders are most common in extreme market conditions where positions need to be opened or closed rapidly, regardless of cost sensitivity. In traditional markets, IOC orders are often used when chasing price limits, while in crypto, they are frequently employed during sudden volatility events.

 

Summary

• Post Only → Maker orders only, fee advantage, no guarantee of execution.
  
  
• FOK → Must be fully filled immediately, otherwise canceled. Best for scalpers and illiquid markets.
  
  
• IOC → Executes immediately with partial fills allowed; remainder canceled. Useful in volatile or fast-moving markets.
  
  

 

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