A Fill-or-Kill order must be executed immediately and in full at the specified price, or it is canceled entirely — there's no partial fill. It's used when a trader needs an all-or-nothing execution, typically for larger orders where a partial fill would leave an unwanted, smaller position.
FOK orders are more common in institutional and futures trading than in standard retail forex platforms, where market and limit orders dominate.
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Guide
What Happens Between Clicking Buy and the Fill
Six things happen in the fraction of a second after you confirm an order, and almost every complaint about execution is really about one of them. A walk through the sequence, step by step.