A-Book vs. B-Book Prop Firms: What Traders Must Understand About Execution Models
In the world of proprietary trading, the terms A-Book and B-Book describe a firm's fundamental business and execution model. An A-Book prop firm operates on a Straight-Through Processing (STP) model, passing trader orders directly to a liquidity provider and profiting from commissions or spreads. A B-Book prop firm acts as the counterparty to its traders' positions, internalizing the risk and primarily profiting when traders lose money. Understanding this distinction is critical for traders selecting a firm, as it directly impacts incentives, trading conditions, and the firm's relationship with its traders.
