A marketable order can fill immediately against existing liquidity; a non-marketable order rests in the book waiting for a counterparty. The distinction explains why some orders fill instantly and others wait.

What makes an order marketable

An order is marketable if its price crosses the current market — a buy at or above the ask, or a sell at or below the bid. It meets existing resting orders and fills right away. A market order is always marketable; a marketable limit is a limit priced to fill now.

Non-marketable (resting) orders

A non-marketable order — a buy limit below the ask, or a sell limit above the bid — doesn’t cross the market, so it rests in the order book as a bid or offer, waiting for someone to trade against it. A mid-price order is typically non-marketable (it waits for a fill at the mid). It provides liquidity rather than taking it.

Marketable = “I’ll take what’s there now.” Non-marketable = “I’ll wait for my price.” That’s the whole difference between an instant fill and a resting order.

The takeaway

Marketable orders prioritize speed (take liquidity); non-marketable orders prioritize price (provide liquidity, save the spread). Scalpers balance the two based on whether speed or price matters more on a given trade. It’s the same tradeoff at the heart of every market-vs-limit decision.