Interactive Brokers LLC (IB) is a U.S.-based online discount brokerage firm. It is the largest US online brokerage firm by number of daily average revenue trades; it also is the leading forex broker. The company is headquartered in Greenwich, Connecticut and has offices in Chicago, Hong Kong, Shanghai (a representative office), Sydney, and Zug. It is a subsidiary of Interactive Brokers Group, Inc., which has offices in thirteen countries.IB is regulated by the U.S.