You CAN use this on a Mac. When you purchase the game, Amazon will take you to a link to download an .exe file that will tell Steam that you have a valid product key. However, if you open the order confirmation email from Amazon, you will find a link to "You Games and Software Library." When you go to that page, you will see your product key for your digital copy of the game. Simply download and open Steam for Mac, go to your Games Library, and click on "Add a New Game" and enter your product key. Your game will start downloading through Steam!