Crypto glossary
Time in force (GTC, IOC, FOK)
Time in force is the instruction that sets how long an order stays active, such as good-til-cancelled, immediate-or-cancel or fill-or-kill.
Every order sent to an exchange carries a time-in-force setting, even if the trader never sees it. Good-til-cancelled (GTC) keeps a limit order on the book until it fills or is cancelled, and it is the usual default. Immediate-or-cancel (IOC) fills whatever it can at once and cancels the rest. Fill-or-kill (FOK) must fill completely and immediately or not at all. Some venues also offer good-til-date or post-only variants.
These settings decide how an order interacts with liquidity. Arbitrage and trading bots favour IOC and FOK because a half-filled leg can leave them exposed, while longer-term traders rely on GTC orders that wait for their price. On crypto exchanges, where markets never close, a GTC order can sit for weeks.
Forgotten GTC orders are a classic mistake: a buy left far below the market can fill months later in a crash the trader no longer expected. Exact definitions and limits vary by exchange, so the platform documentation is the reference.
Example
A bot needs to buy exactly 2 BTC at one price to complete an arbitrage, so it sends a fill-or-kill order. The book only has 1.4 BTC at that level, so the whole order is cancelled instead of half filling.