What is the difference between American-style options and European-style options? American style options are only legal in markets located in the United States, but European-style options are legal anywhere in the world. American-style options are only valid for U.S. equities, but European-style options are used for commodities only. European-style options can be exercised at any time, but American-style options can only be exercised on the day of expiry. American-style options can be exercised at any time before expiry, but European-style options can only be exercised on the day of expiry.