Interactive Brokers uses its SmartRouting system to determine the best execution venue(s) for each order. For some products, IBKR customers may directly route their orders to a particular market of their choice. IBKR also operates an Alternative Trading System (ATS) in accordance with SEC Regulation ATS, on which it executes IBKR customer trades against each other or against one or more professional liquidity providers who send orders into the IBKR ATS. Order executions on IBKR’s ATS eliminate exchange fees and may offer price improvement compared to the NBBO.
Find more information on the IBKRATS orders page of the IBKR website.